As someone that started with 300/300 and went via 1200/75 to 9600 etc - I don't believe conflating signalling changes with bps is an indication of physical or temporal proximity.
Like it was more common than confusing Kbps and KBps.
I mean, the 3.5" floppy disk could store 1.44 MB... and by that people meant the capacity was 1,474,560 bytes = 1.44 * 1024 * 1000. Accuracy and consistency in terminology has never been particularly important to marketing and advertising, except marketing and advertising is exactly where most laypersons first learn technical terms.
Anyway, I didn't think my throw-away comment would engender such a large response. I guess we're not the only olds around here!