Well, spring in New England means that the temperature has always changed recently

. It was chilly this morning and I couldn't start the heat with either the app or the remote while it was still plugged in (@120V). After unplugging, I could now use the app to start heating and, as expected, start draining the battery. After 10-15 minutes, I tried plugging back in and now it continued warming while maintaining charge.
So, with the current version of the app, I can unplug, then start heating and then plug back in to stay charged. Less convenient than a scheduled conditioning available with 120V before, but better than nothing. Maybe Honda will update the settings again so you can always use 120V to maintain SOC during preconditioning. Or maybe I'll have an L2 charger by next winter.