From what i read about it, Apple has a walled garden but charges a flat fee for everyone and has no special deals. Everyone pays the same and they make a little money off of the store but also the hardware sold.

Whereas Google has been caught treating certain parties differently, such as Spotify, something called Project Hug, where they gave extra benefits to parties at risk of leaving the play store, among other unequal dealings.

So the crux of the question is not about the monopoly itself, but the fact that Google is treating market players differently and throwing its weight around to influence the market to its advantage.