What you're referring to, I'd call a historical archive, containing many backups.

When I think about a backup, I'm thinking in terms of recovering last good state after a drive failure or catastrophic filesystem corruption. I don't tend to think of a backup as implying a deep history unless that part is explicitly stated. That distinction was easier to notice back in the days of backing up to tape or optical discs - you don't expect each tape/disc to contain a version history, just a single snapshot, and you don't expect your collection to retain long-gone files unless it's an ever-growing pile of tapes/discs.

In that mindset, it's not reasonable to expect that a backup service necessarily provides the full historical archive.