I expect macOS is cheaper to support and develop for (if for no other reason then because it's a well supported Unreal Engine target) and judged to be, at least potentially, more profitable. But I imagine the relationship with Apple carries a huge amount of weight in a decision like that as well, and I can't even guess how that factors in.
UE supports Linux (via Wine/Proton) just fine. There are tons of games that use it. The main issue is the anti-cheat solution, which does support Linux, but needs to be enabled (they have not). While I am sure there would be issues beyond that, they would almost certainly be minor.
> at least potentially, more profitable.
This is because MacOS is more widespread as a general purpose desktop operating system. Those statistics are irrelevant here. Linux is a more widespread gaming operating system. Dogma is pointless drivel.