Not quite. In economic terms, if:
> Apple is getting more than 100% of the ad revenue Google earns from iPhones
This would mean that Google is pricing it not just "below market value", but also "below marginal cost of production". You can price below market value and still make a small profit. But in your hypothetical it's literally bleeding money.
I don't think it invalidates your point that "it could qualify as a monopolistic practice". But it's an important distinction because generally selling your goods/services below the supplier's marginal cost is inherently unsustainable.
https://thecounter.org/coca-cola-frito-lay-mars-real-estate-...
https://www.vox.com/2016/11/22/13707022/grocery-store-slotti...
At least the other OS's allow you to run your own rendering engine