I should know this by now, but what is the whole process for going from Juniors to Seniors internationally? Doesn't the USFS have to approve and award the assignments?
Nathan is 17 now, correct? Didn't Jason Brown and Joshua Farris turn 18 before they were assigned to any Senior Bs or GPs? And that was after they both medaled at Junior World TWICE, right? Was that purely the decision of Team Kori/Christy & Damon or did USFS mainly decide for them that they would go back to JGPs for another year? And overall, was that a good idea?
Career trajectories were also different, FWIW.
Nathan was 10 years old when he hit the Novice level in 2010 (and won). Jason and Joshua were 14 years old when they were in Novice just a year earlier.
Joshua entered the JGP in the 2009-2010 season (age 14) right after winning Nationals as a novice, finishing 4th and 5th in his two JGPs. At the time, Joshua was quite advanced as a novice, having won by a million points with all his triples (except for 3A). He did four junior seasons (2009/10-2012/13) internationally, though competed as a senior nationally since the 2010-2011 season.
Jason's debut on the JGP was the following season, 2010-2011 (age 15), after he won the U.S. title at the junior level with all triples except for 3A (in Novice, his hardest jump was a 3L). He also did three junior seasons (2010/11-2012/13). Like Josh, he debuted nationally in 2010-2011.
Nathan was too young for JGP, so didn't debut JGP until the 2012-2013 season (age 13). He won JGP Austria with a 3A and backloaded programs, but then his injury (the first) kicked in and he W/D from his other event. He finished 3rd at U.S. Nationals in the junior level, behind Vincent Zhou (too young for Jr. Worlds) Shotoro Omori (who swept the podium at 2013 junior worlds with Josh and Jason). In 2013-2014, Nathan did a full JGP season (+JGPF winning bronze) and won his second U.S. title as a junior and sent to junior worlds, winning bronze. He did one JGP 2014-15 before debuting at nationals as a senior and then went to Junior Worlds, finishing 4th. We all know he did a full JGP season this past season, but didn't do Jr. Worlds/Worlds due to injury. So he was on the JGP four seasons (like Josh) and two world junior championships (like Jason), but only did two full JGP (i.e. 2 events) seasons due to injury/by choice.
Basically Nathan got in the pipeline at an earlier age, but ended up at the junior level for just as long as Josh and Jason.
ETA: Nathan could have entered seniors as early as the 2014-2015 season, since he turned 15 (May 2014) before the July cutoff. If you recall, Nam Nguyen (2014 Jr. Champ) and Adian Pitkeev (2014 Jr. Silver medalist) made their senior GP debuts. Shoma Uno (2015 Jr. Champ; 5th in 2014) and Boyang Jin (2015 Jr Silver medalist; 6th in 2014) made their senior GP debut last season. Despite not making his debut sooner, he will still be one of the youngest guys on the GP circuit at age 17. Sota Yamamoto is probably the only one who is younger (16). Deniss Vasiļjevs is only a few months younger (he'll also be 17 when he debuts on the GP). DAniel Samohin, the reigning Jr. champ will be 18, so the same age as Boyang and Shoma.