It's not p2p. 2 transactions happen: you pay patreon, patreon pays them.

likewise with venmo, no? who gets to decide what constitutes a transaction

If we're being honest, private backroom deals based on a variety of business factors and debates. Venmo is Paypal, Paypal has Musk's and Thiel's deep pockets. They can and will settle something.

There is no real line, just imaginary ones apple draws arbitrarily.