Throw in SCCS, on SCO Unixware, and Darcs, and you match my exposure too, mostly. Now I remember what an abomination VSS was - with the mandatory locking behaviour.
They called it "multiple checkout", and the manual strongly recommended you do not turn it on.
The software had issues with corruption due to operations not being atomic.
It was literally less functional than copying to a shared drive. Of course management and other developers refused to believe that OSS solutions were better, MS ecosystem developers were an extremely insular group.