Hmm true that! Micromys wheel mode seems to require a driver but yeah seems connection to another joystick post is not necessary unlike in example I found from Aminet.
Probably Micromys multiplexes wheel events to XY-movement events then and drivers will decode them. Very cool actually. But since Rys MKII does not have any drivers available, it just cannot do the same sadly (but with new firmare and a driver perhaps it COULD, developer would just need to implement such support) :/