I looked around the other teams and also bought the editor and... yeah, it does appear this isn't just an Omiya thing. I spotted Naoki Inoue and Daiki Kogure from Blaublitz Akita having their 2024 moves in their January 2023 bio for one.
It's like Real World mode has tried to invade Original, but then looking at the 24.3 database and seeing the February 2024 Omiya squad it's like I've got FM25 early or something, though if that were actually the case I would have Arthur Silva on my save (he's still at Kataller Toyama, bio mentions last moving to Omiya in 2023).
Figuring this stuff out is liable to produce a headache
EDIT: So playing Your World mode actually clears up the career stats, though everyone still has the relegation milestone and Miyuki is still erroneously at Chungbuk Cheongju FC. Seems more like a bug then a data error (excluding Miyuki) at this point? First time I've ever been in on the ground floor of a FM game so I've never been frazzled by a database change. Still, can't have ingame records and milestones for things that haven't happened yet or perhaps won't at all