They still have a lot to learn; but you know, when they get the opportunity, they'll know they earned it.
They only "earned" it, just like H/D and C/B only "earned" it if the assigning Fed decides that's the way it determines spots. Other Feds use Euros/4C's as skate-offs, monitoring, or the spread the wealth of WS points, which became crucial to starting orders. And Feds can change that strategy, just like the Canadian Fed is doing in Ladies this year to select its Worlds team.
For a counter-example, there's Gilles/Poirier. They missed the Olympics in 2014 and then went to 4C's, where they earned a bucket of WS points, which put them skating in the second half for Worlds 2014, while their main rivals, Paul/Islam, who went to the Olympics, skated in the first half, just like in the Olympics, drawing 16/32 teams in the SD. G/P drew 30/32. G/P put over a point between them in the SD to land in the penultimate group for the FD, while P/I skated in the group before the ice cut. G/P beat P/I by over 5 points in total, and that established the internal and international hierarchy, Gadbois or no Gadbois.
All three of C/M, C/P, and P/P will lose most of their WS points from junior championships at the end of this season, between 2016-17 dropping off and 2017-18 being factored by 70%. That puts them at a great disadvantage for GP RD starting order next season, where C/M started 9/10 at both of their GPs this year, the Parsons 7/9 and 7/10, and C/P 6/10 and 9/9.
Federation strategy doesn't have to be only "Which Pair can help to get us two spots back?"
ETA:
Aside from U.S. teams likely wanting the additional comp experience, and let's not forget that rankings points from 4CC can help boost or maintain a team's grouping in the RD draw at Worlds, with 4CC being in the U.S., I'm sure USFS wanted the top teams there.
H/B are currently 12th in WS, 8th when you remove T/M, the Shibs, B/S, and C/L. They are assured a spot in the penultimate group at Worlds, regardless of 4C's assignment. It would take a very unlikely combination of events with H/D, C/B, W/P, and G/P there for them to earn enough points at 4C's to get into the last group. They need to be worrying about FB/S, IMO.