If it was cleaned then hair would be removed and it could be assumed that if any is left there was probably more of the same type of hair befoe cleaning."
I have heard of no reliable evidence that indicates it had been cleaned to any degree and in fact, there is evidence and testimony to indicate that there was not a serious cleaning of the MH attempted.
If all the dog and human hair that was found was the result of it having been left over, after a cleaning, then, IMO, the MH would have had to have been a literal mass of hair, prior to any such hypothetical cleaning. Again, that's JMO.
Vaccuming would be normal and would suck up hairs. Washing the floor too. These are normal parts of finishing a trip. If he had time to do his laundry he certainly had time to run the vaccum, wash down the shower,toilet and hard floors.
This would still leave old hairs that have accumulated in out of the way places but pick up new hairs in normal traffic areas.
Again, the interview DW gave to Det. Redden has been entered into evidence. I don't know why he wanted to convey to the police that he cleaned the MH, but he did. Whether he really did, or just wanted the police to think he did, I have no idea. But, as I pointed out earlier, DW himself is on the record regarding this issue.