I'm happy to report that the Ernie Ball VP Jr 25k ohm (log pot) (P0 6181 made in Malaysia)
does indeed work perfectly out of the box. It also looks extremely smart in my humble opinion.
It's well constructed and light in Aluminium and can be cabled to do other things
Like being a volume pedal, with a spur out to a tuner.
The tuner question is redundant in this discussion as you will have one built in to the M5!