The onscreen keyboard while using the Magic Keyboard was an issue for me on the 14.0 GM build and disappeared after updating to the official release.
Maybe 14.2 was forked off the 14.0 GM before additional fixes were sneaked into the 14.0 official release + 14.0.1.
Could be. I saw this issue with the last beta or two of the 14.0 build.
Interestingly when I use my Logitech Folio I do not have this issue. Just with the MK.