That was true at the system level on ITS, file and command names were all 6 bit. But six bits doesn't leave space for important code points (like "lower case")

That was true at the system level on ITS, file and command names were all 6 bit. But six bits doesn't leave space for important code points (like "lower case") needed for text processing. More practical stuff on PDP-6/10 and pre-360 IBM played other tricks.