Yes I’m afraid so, because selling a house does not fall under extenuating circumstances; you plan to sell your house it doesn't just happen out of the blues so you should have planned alike and blocked dates in order that guest do not book your accommodation. It is unfair to the guest to suddenly lose this booking because a host didn't draw a line but continued to take bookings on the off chance that the house did not sell by that time.
Likewise if a guest cancels under non extenuating circumstances, they get penalised also and lose their money - it works both ways and is in the terms and condition agreed by all guest/ host prior to joining Airbnb. The host choices which level of cancellation policy to apply to their listing, the penalties are clearly confirmed.
It’s a hard lesson to learn…..