> 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