I had imagined this was merely theoretical, but learned that there are computers implemented with a single instruction.

https://en.wikipedia.org/wiki/One-instruction_set_computer#M...

https://esolangs.org/wiki/OISC

In the functional realm which LISP inhabits, two combinators suffice: S and K.

https://en.wikipedia.org/wiki/SKI_combinator_calculus

in the context of S and K, lisp is not functional

I don't think movfuscator proves you only need one lisp primitive. Just that any language can be evaluated using mov's many variant forms.