My friends and I play Apex through Steam, which I downloaded for free. When you click to purchase "Apex coins", it takes you straight to EA's website. Apple wants to enforce a cut on every purchase of in-game currency. Steam does not do this.
And Valve allows you to sell steam keys on your own website also without paying the cut, so long as you don't undercut the steam store.
They take a cut for microtransactions that they process, but you are free to use your own service. They do require price parity. That link doesn't seem related at all.
Do you have any sources on how restrictive valve are or have been with that, or is that just speculation? Can developers default to their own payment systems and bypass valve's, or is theirs required to take a secondary, less-accessible option (when it's even allowed)?
And Valve allows you to sell steam keys on your own website also without paying the cut, so long as you don't undercut the steam store.