I don't think it's fair to go after TT on what they say day 1. Every scientist normally works from a "hypothesis" and then tests this - TT just expose some of their thinking during the programme so there are bound to be times when initial assumptions get shown to be wrong. The alternative would lose the "your watching it live, warts and all" approach of the programme and make it probably less popular?
I remember the roman bridge timbers show (peircebridge?) where the tree-ring guy refused to show a potential date mid programme (haven't seen him back since :-) ).
I've watched lots of TV programs dumb down science over the time TT has been going - I think they've managed to keep the quality up all things considered.
I think TT bridges archeology and TV reality program rather well and TV would be a sadder place without it for me.
Mac