I agree with you that the best fix is to take into account the type of turf/plant and its water requirements during dormant times. I think Rachio might also, but their answer is likely that keeping up with all the different turf types and regions to make the adjustment is too much for the program at this time.
Your suggestion of a “dormant” mode override per zone might be good. If I only had to switch this one switch each year I would be happy. I haven’t even considered my shrubs in all this… hmmm.