I mean, it probably was a branch that several people contributed commits to that was squashed prior to merge into mainline. Folks sometimes have thoughts about whether there's value in squashing or not, but it's a pretty common and sensible workflow.
Perhaps "common and technically works" would be a better way to put that (similarly for rebase). I suspect people would stop squashing if git gained the ability to tag groups of commits with topics in either a nested or overlapping manner.
