Expressive Instruments: individual note velocity cannot be adjusted

WIN7; MS 3.6.2; MuseScore_General_HQ

I have a score that contains a 'cello section playing chords written into a single staff. Some notes in the harmony should be quieter than others. Although I can adjust the velocity of single notes within a chord using Inspector or Piano Roll Editor, there is no change in loudness. (PRE does report the adjusted velocities as they were input.)

However, if the Instrument is changed from "Celli Fast Expr." to "Celli Fast", manually overridden velocities become functional.

Is this intentional?

Thanks,
z