In 2016, that laptop also came with System Integrity Protection - you couldn't change /usr/bin/python if you wanted to. And you still can't to this very day. Changing System-provided python was always against recommendations in prior OS versions because the next OS update could re-replace it at any time.

I agree that it probably contributed to python 2 inertia as it was re-exposing people to the idea that "typing python in the Terminal gets me python 2" and "I just used what I already had" - but it definitely wasn't stopping people installing a newer version.