Decisions are made based on business.
Will a switch to a custom Apple that takes capacity, design engineers, validation, test and valuable TSMC capacity enable more sales and profit and is it strategic?
Or is it easier to go to BK with that "threat" of going internal to get amazing pricing, it is amazing pricing and the Intel team's silly antics to keep the account.
Whether the MAC uses x86 or internal won't move the MS by more than a few tenths of a point, nor would a few % in performance nor a few minutes in batterlife matter either.