I-Master Inhibitor Release

Hi, - I wanted to check in on some behavior I wasn't expecting and maybe I'm missing something I don't understand.  The scenario is I have a group of lights running an effect, I have them on a I-master sub.  I then want that sub to be an inhibitor for their cue state instead, I switch to inhibitor.  The fader works as I'd imagine, inhibiting the intensity channels and nothing else. At 0 it's 0 at full it's restored.  The part I wasn't ready for is that when the bump button is pressed in I-master mode it inhibits and won't release.  Only changing the mode to proportional or back to an additive sub will restore the lights.

Am I missing something about how an inhib with I-master should work?