[OnePlus 6T  Guides, News, & Discussion] runningnak3d:
Whoa, I was in the wrong directory -- they most definitely are signed with different certs:

International version:

-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----

TMO version:

-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----

If you flash any of the RSA signed firmware from the international version onto the TMO version you will get "mismatch" bootloop...

-- Brian