I tried a couple of times but I didn’t receive any daily update after I reached 20 hearthlings 
Also tried resetting the configuration to default, but it was the same. And declining at 19, but the next day I got another daily update.
I don’t doubt that you experienced that bug, I just haven’t seen it yet. Maybe you declined something else?
There’s a strict requirement when the encounter happens, just waiting to hear if someone else also experienced it, since at the moment I can’t reproduce it.