Down in the basement of Apple there will be concurrent MacOS development on Intel and Apple's ARM chips. These comparisons with MacOS don't take into account that it's largely been around for years now. A next generation system will be coming at some point, which would be a good candidate to buildup on new chips. Pro users aren't exactly the main customers at Apple anymore, actions speak louder than words and Pro hardware is years between updates. If they made these changes, it's less about exceeding 1:1 marketplace performance and more controlling end-to-end the hardware/software union.
Apple wouldn't have any intention of switching the Pro computers to ARM anytime soon. The Air and MacBook would change first, Pro later (maybe much later). General consumers are mostly using their Air and MacBooks for the same things they already do on their phones and iPads (email, Facebook, browsing, instant messaging, Word, Excel etc) hardly taxing. If they were building a next-gen desktop OS there would be no comparison, we couldn't know how optimised it could be. I'm also not suggesting it would be an iOS shoe-horned onto a desktop, but purpose built largely from the ground up as the next MacOS.
Lets not forget that ARM already has a few toes stuck in the MacBook Pro's to power the Touchbar, it's a very small start, but it is there in the MacBook Pro right now. Future versions may change the ratio of work between Intel/ARM.
Maybe a developer might also comment if it would be easier to develop for all ARM chips at Apple comparing to the current Intel/ARM setup.