A Sid Caesar skit showed doughboys celebrating and one shouted "World War 1 is over!"... when they made GPLv2 maybe they didn't anticipate creating future versions (although yeah, if you're already on v2 you should foresee that).

There is a GPL v.1, and it may have been so numbered at initial publication:

<https://www.gnu.org/licenses/old-licenses/gpl-1.0.html>