I tried this now in my environment and it works as it’s supposed to do.
Even if I have not worked intensively with layout XL over the last couple of
years I wouldn’t expect the tool to behave different.
Why the m (multiplicity) factor is treated differently form other parameters like width, length or number
of fingers, which are all updated with the "update layout parameters", is because m defines a m times physically
separated devices in parallel. In this case it is an extra component and some extra nets, parallel wiring for S, D, G for e.g.
a MOS device. So you need in fact "update components and nets".
This should it make more clear.