Since the last download when doing a workout in erg mode Zwift is controlling the trainer, in my case a Tacx Neo 2, based on the output required for the segment. Previously output was controlled by shifting to an easier gear or a harder gear depending upon what was required. Is this by design?
Sounds like previously you weren’t in ERG mode. You probably didn’t have the Neo2 paired as the “controllable trainer”.
If paired properly, when doing a Zwift workout, ERG mode will control resistance relative to your cadence to meet the power target and thus you will not need to shift.
Erg mode is designed to work via Zwift controlling the trainer resistance to achieve the required watts output regardless of gear or cadence. If this was not happening prior to the last update either a bug was corrected for your trainer, or erg mode was not enabled previously.