Did some more reading, I was probably thinking of broadcast TV signals, which were 25 or 30 fps because one frame is two fields. and I wrongly assumed CRT TVs could only do one thing, but consoles mainly did progressive video.

Was it? afaik PAL was 50Hz but 25fps, and NTSC was 60Hz at 30fps. Two periods per frame because of interlacing or something like that.