That so many artifacts found in Tut's tomb belong to others opens two possibilities.

One, he died unexpectedly and other tombs from the family were raided to make his burial complete

Two, the artifacts belonging to others came from robbed or destroyed family members' tombs and were gathered in Tut's for safety/familial reasons.

As for the theory, a sample of 1 being used to determine the sex and identity of the unknown people on the Berlin stela is a dangerous step to take. It could just as easily be Akhenaten and Nefertiti, or many other combinations.

Smenkhare is the Joker in the pack. He existed, and like others I accept that he is KV 55. The original estimates of age at death make him far likelier than not to be Smenkhare. Unlike Hawass, there was no one shoving an agenda on the body. Now, if I am wrong and that really is Akhenaten, then we still have to explain Smenkhare. I dunno, I just find the 'pin the name on a woman' game that has been played incessantly to be, shall we say, unproductive.