Observation:
Until version... at least 4.7.8* and how many version after, I don't know (because I only notice now, at 4.8.7) the structure of folders used for profile picture uploads was in this format:
/file/pic/user/year/month/pic.xxx
now is:
/file/pic/user/pic.xxx
so practicaly, no more year and month.
Problem:
The new structure format, in my opinion and in a logical thinking... it's not good at all and can cause problems on long term.
Why?
Because uploading all the profile pictures in the same folder, especially on big communities, makes that folder huge (many file in a single folder). For example, on my server, that folder, already has more than 65.000 photos and any FTP/SFTP client barely opens/list it.
Others:
I've saw that timeline photos and other are still in old style (year/month), which is good.
*As far as I can see, the old format stopped for me in 06.2021 (the last folder) but I don't know which version I had then (not to old because, I usually update when a new version appears). I mentioned an older version above, because that version I had on a test/development server (which was not updated from initial install) and I can confirm it was that way (the old format).