Earlier quoted context omitted.
Then why go to the trouble of archiving them, then upload them to a public archive site, only to then keep them secret? I'm sure pastebin is filled with people's AWS credentials, too, but you don't see them randomly denying access to listings
Because then you can access the archived destination if you already know the short URL. You just can't get a full list of potentially sensitive short URL/destination pairs.
The sibling link above that queries Wayback's warc index shows at least the first several are only 6 alnum wide so it's no wonder the ArchiveTeam got them in reasonable time
Picking one at random, it seems the super sekrit deets you're safeguarding include buyrussia21.co.kr which, yes, is for sure very, very secret