OP is the correct answer. The reason vampires can't enter homes is because of the positive mental energy built up around the house as a threshold. Giving consent to a vampire to enter is allowing them a pocket through the threshold. Said threshold is built up through regular living. A family home with a stay at home mom and three kids will have a stronger threshold than an apartment lived in by a two-job worker. Some stronger vampires can break through weaker thresholds (depending on source). There are multiple supernatural beings that this threshold can (supposedly) stop, not just vampires. So just because someone else tells them they have legal permission to enter a home doesn't mean they'll be able. It's magic, not legality.