It makes perfect sense. Thor's scruple was that Vaughters wouldn't put all of his eggs in one basket during a race (specifically the classics), and preferred to improvise on the road. Thor wanted a team that would plan to work for him 100%, and stick to the plan. Being on the best classics team also meant that Thor had more teammates who were contenders to take the win instead of him, especially with Vaughter's improvisational tactics.

Whether he gets what he wants will be seen. Hincapie is always a contender, but also selfless. If Gilbert hops on, that'll change things too. I personally think Gilbert and Thor have different enough strengths and weaknesses to race classics together happily and effectively.