The versions were indeed complete files and not deltas. The limit to the number of files kept was a user-configurable setting, and there was a series of comman

The versions were indeed complete files and not deltas. The limit to the number of files kept was a user-configurable setting, and there was a series of commands (like PURGE) to get rid of unwanted versions. (There was also an optional directory size quota, to limit disk usage by users.) Obviously, it would take a bit of jiggering to alter the system to use deltas-- but you'd think that there would have been ample opportunity in the past few decades for someone to do that work, if desired.