I remember that too - from about 1979. 12 speeds would have been unusual in a sport bike then. 5 speed/120 was still dominant. 6 speed was an extra trick set up that a few racing bikes had - kind of like 700c training wheels...

FWIW- my 78 Masi was originally a 10 speed (so I was told), but had been re-spaced by the time I acquired it about a year and a half later. By then pretty much every one with a racing bike was using 6 speed/126.

I re-spaced a whole lot of frames from 120 to 126 back in the early 80s at my after school LBS job.