I think the situation with the US dance JGP's is that they don't have anyone else to send.
Looking at last year's national results, of the 13 teams that competed in Junior, only Samuelson/Bates and Bosley/Corona are age eligible. Everyone else is too old (Davis/White, Miosi/Ponomarev, Huber/Edelmann, Elliman/Serebrenik), or broke up (8 out of the 13 teams who competed in Junior broke up).
Of the 12 teams that competed novice last year, 4 (including Tomarchio/Sinchek) are on the JGP, 6 broke up, 1 is age ineligble, and 1 stayed novice (Deutch/Lorello, and I'd be surprised if the USFSA would give an assignment to the 11th place novices anyway). After monitoring at Lake Placid (and the NAC), a new team (Oswald/Withrow) and a team that didn't make it out of sectionals (Cohen/Roberts) got a JGP event, and neither of them did well enough there (I think depending on the event, the team has to either finish in the top 4 or top 6) to get a second assignment.
So for the last JGP, the USFSA could either have put those two teams out there again, or hope that the novice bronze medallists have recovered from their injury.