The metadata appears to be preserved on papers from sci-hub. since it works by using harvested academic credentials to download papers, this would allow publishers to identify which accounts need to be closed/secured
https://twitter.com/json_dirs/status/1486135162505072641?t=Wg5XAzujycz79Cop_ap8vQ&s=19
for any security researchers out there, here are a few more "hashes" that a few have noted do not appear to be random and might be decodable. exiftool apparently squashed the whitespace so there is a bit more structure to them than in the OP:
https://gist.github.com/sneakers-the-rat/6d158eb4c8836880cf03191cb5419c8f