Re: Timing is everything - hourglasses question
"Is the correspondence with the 5v logic standard just coincidence?"
Probably yes. Other logic voltages were 10V and 12V (used with CMOS) and even 15V with a short lived industrial noise tolerant logic system. 5V didn't last all that long, either. Once HCMOS came along voltages started to drop fast.
I think it had more to do with being the lowest voltage that gave a good power/speed tradeoff with ttl.