Oh, sorry, I agree. I thought you were disagreeing with parent; saying "it doesn't run arbitrary executables, it only runs linux executables".
Although actually, I see what you mean now. D'oh. Windows was so far out of my mind I wasn't even thinking of it as a distinction to be made.
Arbitrary Executables = Arbitrary Linux Executables.
Since Python3 runs on linux, you can invoke python3 scripts.