This isn't to say that Windows games built on these engines aren't entirely running on DX12 code either. I think most games these days give you the choice to pick your graphics backend. It's an impossible ask, but I'd love to see what the stats are for Unreal/Unity graphics API usage across games.
That being said, on the iOS/macOS front, I don't know what these games are using to deploy to that platform. It could be that they use MoltenVK, but I could also see them using OpenGL or their own Metal rendering pipelines. As someone who grew up gaming on a desktop PC, I forget that smartphones and tablets are the future of the gaming industry. It felt weird to see Apple showing someone sitting on their couch with their iPhone 15 connected to the television, playing No Man's Sky via bluetooth controller, but simultaneously really cool.
It appears to me that languages born out of a design-by-committee process struggle to make anyone exceptionally happy, because the only way the language moves forward is by keeping all of its members equally miserable, or my masquerading as one language when in reality it's closer to five different languages held together by compiler flags and committee meetings.