Posted here hoping maybe somebody had some idea, but I have kind of the same problems as posted in this post: Please don’t forget to fix transmog too! - WoW Classic / Cataclysm Classic Discussion - World of Warcraft Forums (blizzard.com)
After some further checks over the weekend, it makes even less sense to me. Items I know I have picked from quests this year, but before the prepatch, are not showing up, like the axe from Outland’s Ring of Blood, while items from quests I did at the start of TBC are, same with how some items, like T5 and kara tank shield, I can see while I haven’t had them in my inventory for nearly 3 years, but stuff from just from just before prepatch is not showing up.