If USFS really looked at numbers and momentum over the course of the season, then C/B should be doing the FD b/c they got the highest score of the U.S. teams at both GPF and Nats.
They got the highest scores at GPF and Nationals doing their best with the Shibs faltering. The Shibs could falter again, but their SB from two weeks before GPF is still higher than C/B's FD score at GPF. I think H/D's FD is the best of all three, and they have the second-highest FD score, but I'm not sure the judges agree, and they could be sacrificed easily for B/S in the TE, especially.
From a bureaucratic point of view, choosing the Shibs for both and making C/B and H/D hungry, and possibly angry, like Sotnikova was, is better than choosing between the team with the higher recent FD, although different by a small margin, and the National Champions, whom I would have chosen. This isn't like 2014 Ladies, where Edmunds was clearly not in the running for the TE.
I disagree that, if true, the decision is only based on singles vs. ice dance. Both D/W and V/M were clear in 2014 that they wanted to go skate both, and I think part of this was because they wanted to face-off in the TE for both programs. And while Chen has a higher potential upside than any current US Dance team in the individual event, with V/M and P/C clearly ahead of all, his potential downside in the individual event could look like Helsinki, given the risk and difficulty he brings and momentum Jin, Uno, and Fernandez are bringing from 4C's and Euros, plus Hanyu being the warrior he is, although his physical shape is unknown, and never knowing which Kolyada will show up.
The US could be scrambling for bronze in the TE, or they could be fighting for silver. US Dance is a better points-getting bet, at least on paper, than Men, especially with Chen splitting.