I think this is more of a nudge to Slack and Discord (and certain others) to make their Mac apps based on their iPad apps instead of Electron. And for some games to add keyboard support.

And once they do, others will follow. Except Google or Facebook, which will remain website-only because their whole businesses is based on ad networks across the web.

I don't think iOS apps that have poor UX on the Mac will be allowed in the Mac App Store long term.