I am already starting to be really upset by this situation, which have been discussed here quite a lot. The over all rating does reflecting at all the category rating, I find it almost impossible to be a sufperhost.
To all of my lower ratings it is the case, examples:
3 star overall for 4.7 average
3 stars overall for 4.2 average
4 stars overall for 4.8 average (this guy is a host which left the house like after a war).
... And I can go on and on.
The final rating the guest is asked rate if it was following their expectations, and if they expected it to be great and found it great they would be ok to give 3 stars.
Average rating is the the best way of reflecting the guest opinions, and is in fact the standard way all other websites use, why not airbnb???