UberXL refuses to take 6 people

So, I ordered an UberXL because we were 6 people. The app shows capacity of 6 people. But the driver then shows up in a Prius Plus. Technically, this model has 7 seats, but it was configured as a 5 seater and the driver stated he was only "allowed" to take 4 people. Had to order another one and support says there is nothing they can do.

Is this normal?