well, first, you profile still says sketchup 2020 on a mac, might be time to update it 
second, occasionally since when ?
if it’s recent, say about month, my guess is that they are updating the warehouse into a 2024 format. meaning that sketchup 24 is around the corner. Last year, 23 was released on feb 16 so it’s not a wild assumption that 24 is near
Although the SU files are versionless since 2021, some elements in newer version might be lost : in 23.1 we saw the snaps appear, I haven’t tried but I suppose opening a 23.1 file with snaps in 21 would give the same message.
SU24 probably brings / changes a little something too. and even though the warehouse files were made without this little something, as they’ll be converted to SU24 format, they’ll display the message.
but, you know, it’s just a guess.