I don't think that the 2 rooms in one is the problem. I have the same problem with this dorm room (that has the same settings as shown above).
It's the booking itself that places multiple people in one bed (as you can see in the picture below, one booking with 2 people are placed in one bed, the other 3 people placed in one bed) even though unit allocation is set on one per guest.
It does work alright when you create the booking by continue and split booking, but that I would like to know if Booking.com and other websites will do this automatically.
