I don't know. It depends how you define "Zero" in this context. There's a huge range of achievement levels on the road between winning the Tour and being the worst pro rider in the world.
My guess would be that he's got too high a proportion of fast-twitch fibres and probably doesn't recover well enough to be fully competitive over three weeks.
Thomas was lead out man for EBH in the 2011 Tour and Cav in the 2011 World RR. Wiggo was "last but 3" in Cav's train in that race suggesting that Thomas is naturally faster than Wiggo over short distances
Whatever lack of competition Wiggo had in the IP, he was very good at putting back to back performances together in consecutive days, suggesting his recovery is "good". (2004 = 4:15, 4:17, 4:16; 2008 = 4:15, 4:16, 4:16).
Or put more simply: Thomas isn't as good a rider as Wiggins.
Who knows for sure? There are far more talented riders than there are major races to be won, so only the select few will ever be big time winners.