Thanks for the comments. This ROOLforum page points to the official documentation:
On 05/11/2022 22:16, John McCartney (j.mccartney) wrote:
In article <5A42B3899D%mik.towse@xxxxxxxxx>, Mik Towse
Scroll wheel support does not appear to work in
emulated hardware like, Virtual RPC or RPCEmu.
That's why I always use the ARM7500 model in VRPC.
It does in VRPC if you use the ARM 7500 model. Although
it doesn't appear consistent which window is scrolled.
I've never noticed any inconsistencies - perhaps because I
always set it to scroll the window under the mouse pointer.