Those are good questions. My take is that it would be similar in spirit to the way government can act to prevent price gouging with drug patents. Notice that platforms are allowed to charge and regulate access to the API, but it has to be "reasonable". Here is what is stated on section 4 on interoperability:

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SEC. 4. INTEROPERABILITY.

(a) General Duty Of Large Communications Platform Providers.—A large communications platform provider shall, for each large communications platform it operates, maintain a set of transparent, third-party-accessible interfaces (including application programming interfaces) to facilitate and maintain technically compatible, interoperable communications with a user of a competing communications provider.

(b) General Duty Of Competing Communications Providers.—A competing communications provider that accesses an interoperability interface of a large communications platform provider shall reasonably secure any user data it acquires, processes, or transmits.

(c) Interoperability Obligations For Large Communications Platform Providers.—

(1) IN GENERAL.—In order to achieve interoperability under subsection (a), a large communications platform provider shall fulfill the duties under paragraphs (2) through (6) of this subsection.

(2) NON-DISCRIMINATION.—

(A) IN GENERAL.—A large communications platform provider shall facilitate and maintain interoperability with competing communications services for each of its large communications platforms through an interoperability interface, based on fair, reasonable, and nondiscriminatory terms.

(B) REASONABLE THRESHOLDS, ACCESS STANDARDS, AND FEES.—

(i) IN GENERAL.—A large communications platform provider may establish reasonable thresholds related to the frequency, nature, and volume of requests by a competing communications provider to access resources maintained by the large communications platform provider, beyond which the large communications platform provider may assess a reasonable fee for such access.

(ii) USAGE EXPECTATIONS.—A large communications platform provider may establish fair, reasonable, and nondiscriminatory usage expectations to govern access by competing communications providers, including fees or penalties for providers that exceed those usage expectations.

(iii) LIMITATION ON FEES AND USAGE EXPECTATIONS.—Any fees, penalties, or usage expectations assessed under clauses (i) and (ii) shall be reasonably proportional to the cost, complexity, and risk to the large communications platform provider of providing such access.

(iv) NOTICE.—A large communications platform provider shall provide public notice of any fees, penalties, or usage expectations that may be established under clauses (i) and (ii), including reasonable advance notice of any changes.

(v) SECURITY AND PRIVACY STANDARDS.—A large communications platform provider shall, consistent with industry best practices, set privacy and security standards for access by competing communications services to the extent reasonably necessary to address a threat to the large communications platform or user data, and shall report any suspected violations of those standards to the Commission.

(C) PROHIBITED CHANGES TO INTERFACES.—A change to an interoperability interface or terms of use made with the purpose, or substantial effect, of unreasonably denying access or undermining interoperability for competing communications services shall be considered a violation of the duty under subparagraph (A) to facilitate and maintain interoperability based on fair, reasonable, and nondiscriminatory terms.

(3) FUNCTIONAL EQUIVALENCE.—A large communications platform provider that maintains interoperability between its own large communications platform and other products, services, or affiliated offerings of such provider shall offer a functionally equivalent version of that interface to competing communications services.

(4) INTERFACE INFORMATION.—

(A) IN GENERAL.—Not later than 120 days after the date of enactment of this Act, a large communications platform provider shall disclose to competing communications providers complete and accurate documentation describing access to the interoperability interface required under this section.

(B) CONTENTS.—The documentation required under subparagraph (A)—

(i) is limited to interface documentation necessary to achieve development and operation of interoperable products and services; and

(ii) does not require the disclosure of the source code of a large communications platform.

(5) NOTICE OF CHANGES.—A large communications platform provider shall provide reasonable advance notice to a competing communications provider, which may be provided through public notice, of any change to an interoperability interface maintained by the large communications platform provider that will affect the interoperability of a competing communications service.

(6) NON-COMMERCIALIZATION BY A LARGE COMMUNICATIONS PLATFORM PROVIDER.—A large communications platform provider may not collect, use, or share user data obtained from a competing communications service through the interoperability interface except for the purposes of safeguarding the privacy and security of such information or maintaining interoperability of services.

(d) Non-Commercialization By A Competing Communications Provider.—A competing communications provider that accesses an interoperability interface may not collect, use, or share user data obtained from a large communications platform provider through the interoperability interface except for the purposes of safeguarding the privacy and security of such information or maintaining interoperability of services.

(e) Exemption For Certain Services.—The obligations under this section shall not apply to a product or service by which a large communications platform provider does not generate any income or other compensation, directly or indirectly, from collecting, using, or sharing user data.