IV heads have the neck and part of the shoulders/chest on the same model, so when the head moves around it doesn't become glitchy/have holes in it (the neck/shoulders stay static for this), however it doesn't have any of that on the shirt/clothing model, Fidox probably just added that to get the geometry/measurements and such right.
Thanks, that's basically what I thought. Say, you know what this Tommy mod needs now? ...3D glasses.
And a sombrero!
Why not throw in a cigar and call it a day?