> "Demands" is not a legally defined term.

“Search” and “Seizure” are, and mandatory disclosures are neither.

> suppose the government created a reporting requirement that required you to divulge all your conversations with your mother yearly by April 20th. Would that be an unlawful search?

No, it would not be a search at all. It would be unconstitutional for the simple reason that it serves no function Congress is affirmatively empowered to do, but its not a search. If asking for iinformation under penalty was equivalent to a search, subpoenas (which are not warrants) would be Fourth Amendment violations, and every subpoena would have to instead be replaced with a warrant.

> "Demand" for material details about your possessions and how you conduct your life is indistinguishable from a search.

A search isn't a demand, a search is when the government accesses your property and looks for the things it want, not when it asks you to provide them. A search is what the government gets a warrant to do if they have evidence you aren’t complying with a legal demand for information or things (, the subpoena for Trump to turn over documents followed by the execution of a search and seizure warrant to look for and take them when the government had evidence that the former was not complied with.) They are very different things.

> By your logic, a cop could go get a warrant to search under your sheets for teddy bears.

They could, if there was probable cause to believe that (1) there were teddy bears there, and (2) the teddy bears there were evidence of some crime. Perhaps more to the point, though, the conditions under which the government could get a subpoena or other non-warrant order for me to turn over or disclose the existence of any teddy bears I have, though, would be much different—and not controlled by the 4th Amendment—than those for which they could get a search warrant.

> You're not getting a warrant to search or probable cause to search on the grounds that someone is in possession of something lawful.

Yes, you can: things can be in themselves lawful to possess, but also be evidence of a crime.

> Participation in commerce with ones neighbor is not activity under the purview of the federal government under the constitution.

Arguing that the Securities Exchange Act, or other laws supported by mandatory reporting requirements, are invalid in purpose outside of the reporting requirements and therefore that the reporting requirements have 10th Amendment issues is a different thing than arguing that the 4th Amendment prohibits mandatory reporting even if the underlying purpose of the law it supported was otherwise within Congress’ Constitutional authority.

> Mandatory reporting is not regulation of commercial activity.

A reporting requirement tied to a particular commercial activity is regulation of that activity. It may not be regulation that you prefer, but its definitely regulation of it.

> Requiring disclosure of private information under threat of civil or criminal penalty is a violation of the 4th.

No, it neither a search nor a seizure, so even if it is not reasonable (which, again, doesn't alaways require a warrant for actual searches), its not a violation of the 4th.