Maybe because he didn't want to travel back and forth to Japan from the USA so close after worlds? Nathan stayed for SOI.
I agree Vincent looked especially strong, technically and artistically, at WTT. Is there any chance he moves to Hamada full time? Obviously, it's a big move, but he's improving and it shows. It will be interesting to see him pushing Nathan now. As we saw at WTT, even one mistake from Nathan leaves the door open when Vincent is clean. US men's skating is certainly strong at the moment!
One mistake from Nathan when he's skating an "easier" layout than he did say, at worlds. His WTT layout was 9+ points lower BV than at Worlds.