I'm not sure about the GT part, but here's some info about Genesect:
The Drives (Chill, Shock, Douse, Burn) give Genesect's Techno Blast. Chill gives Ice-type, Shock gives Electric-type, Douse gives Water-type, and Burn gives Fire-type. The person may be talking about these types, or maybe STAB. Of courese, you can still use Genesect if you wish. Mine was a key in defeating the Gym Leaders. Well, if I get any more info about this GT thing, I'll post. Hope you find my extra info helpful! Sorry about dodging the original topic. :( Oh well.