I had the similar issue, 35 older albums showed as added on that day. You mentioned updating your local library. I don’t recall any library updates here, the added dates just changed and those were all Qobuz albums.
Roon requested I send them the entire RoonServer folder with the catalog. I did that and was told it’s a possible bug they will be looking into and to check the items fixed in future updates to see when a fix is applied for the issue. The ticked is already closed. I’m curious what triggered the change in the catalog. All I can do is wait and see.