6x6 girls was still being played in TN in the mid 70s, when I started HS. 3-3 each end.
If you want to go waaay back, there was a version that was 2-2 on each end and the two centers could only move in a narrow strip from sideline to sideline at center court. The center had to receive the pass from the defense and then pass it to the offense. If you visit some old school gyms, usually in rural areas you can still find floors marked out this way. I used to play on a travelling charity-game media team and we played in all manner of odd rural gyms - wood, tile, carpet, wooden backboards, metal backboards, fan backboards, etc.
Idk It's the way it was played decades and decades ago in many places