This is already the case: the Marzipan apps shipping with Mojave are _shockingly_ bad (Home, News, Voice Memos). Standard keyboard shortcuts don’t work, drag-and-drop is inconsistent, and it’s clear that they never considered standard Mac features like multiple windows while designing them.
I worry that people will look at these badly-ported, out-of-place apps and say “Apple are doing it, so why can’t we?” rather than “Even Apple could only come up with this, so let’s not.”
Apple could get real "real world feedback" if they have released the actual framework, not stuff made with it.
In my opinion apple released them as preview because they have made the apps, wanted to have them in the release, but knew that people would see that they are weird, look into the .app container and see that they are not made using AppKit.
I am pretty sure that there are a lot of hardcore Mac users in Apple and any of them would see that these are not good Mac apps.