I would like to ask a question
To quote "But by making even one FireOS phone, the OEM would have lost the ability to include Google Play Store on its other devices."
Has anybody even seen the Play Store on any Amazon device, as I most certainly haven't, they don't use it as they want all the income for themselves.
So that's a bit of a non argument.
I'm not agreeing with googles business plan but lets at least avoid non existent examples being used.