I remember the transistional period as not sudden. I to this day sometimes will say "apply a 400 cycle note to the input..." But tried to make myself use Hertz. It took time for everyone to get onto the new name for cps. (I do recall cps as more common than c/s.)
Just as the shift from mmf to uuf to pf took a while.
In 1972, in the grand scheme of electronics history, six or seven years is still "recently."