> What I don't know is if the PDP-8 BASIC came before the PDP-10 version.
This was a fun rat-hole. (My first programming was Edu-24 BASIC on a pdp-8/e my 7-12 school had.) It appears that the DEC-10 BASIC is earlier, at least according to how I intuit the timeline from https://en.wikipedia.org/wiki/BASIC-8