I think they're sending the top3 at Nats to 4CC for two different reasons: the first of them is to show their programs in front of the international judges and adjust things if necessary. Josh was injured during the GP season and his only appearance wasn't very good for that reason, and Adam has changed his short program, they need a bit of input from international judges before Worlds. The second reason is also directed towards Adam and Josh: improving their World Standings placements so they get a better draw at Worlds. Adam is currently #21, Josh is #30 (Even though Chan (3), Machida (5), Max (10), Takahashi (11), Ricky (12), Menshov (13), Petrov (16), Jeremy (24) aren't doing Worlds for sure, so virtually Adam is #14 and Josh #22) Euros are this week and the European skaters will improve their placements. With strong 4CC showings they could aspire to skate in the last 2 groups in the short program, and this way getting a bit of PCS help because judges tend to score higher the later into the short they are.
The reason to send Jason, who doesn't really meet the criteria mentioned above (same programs as in the GP season and #14 at World standings, virtually #8 for Worlds) is a bit psychological. He didn't have an outstanding GP season and is in a better moment now. Showcasing that in front of a panel of international judges won't harm him at all.
I agree that Max should deserve something but seeing things with perspective, the decision makes sense. Also Max is currently #10 at World Standings so he won't have any kind of problem getting 2 GPs for next season. And don't forget that 4CC is in 2 weeks, maybe one of the top3 decides to focus on Worlds and decides not to go to 4CC.