It doesn't presume anything of the sort. The dependent intellectual property is still intellectual property and would be subject to the exact same consideration

It doesn't presume anything of the sort. The dependent intellectual property is still intellectual property and would be subject to the exact same considerations. (Per the proposal: If copyright, code for that dependent IP would need to be registered with a source code depository or be subject to forfeiture of said copyright in a court of law; if patented the code would need to be open source and maybe even copyleft to begin with.) The public may need to play whack-a-mole to access the full source code of larger projects, bring dependents and then their dependents and so on to court until the entire thing is open source, but that's still a better deal than the current situation where the public domain is owed nothing ever. (ETA: And "incompatibility between legal regimes" is mostly moot due to the Berne Convention anyway, at least per my lay understanding of it. That said, the proposal is entirely hypothetical and no such legislation would likely pass in any country so worry about international complications is mostly cart-before-the-horse.)