It doesn't seem to be this though... Shoma gets crazy GOE for his jumps everywhere, and so far I haven't seen a single justifiable reason why (the explanation seems to be, because he's "overall" a better skater than everyone else, he gets higher marks for everything. In which case, I say, let's bring back 6.0. What's the point of all this TES/PCS thing?)You have a situation where you got 4 out of the top 10 who competed at 4CC or Euros...I feel there was a bit of a senior pcs boost if they skated relatively clean. This is different from past years where they were at juniors after doing senior GP because they were too young. It was different than Yu/Jin in pairs since they didn't get to do 4CC (and judges didn't really give them that much of a boost relative to Seguin/Billodeau, who had been in juniors all year.
This makes a good case for that "Don't go back to juniors if you did seniors" rule they proposed. Though on the other hand it shuts the door competition wise for skaters from smaller countries who can't qualify for Worlds...
Like you said, Yu/Jin got no boost (and frankly I thought they were underscored in PCS). How is competing in the GP series/GPF less boost-worthy than Europeans/4CC? Also, Adian was at Europeans--he got pretty atrocious marks there and lower PCS than Sasha Petrov here. (I personally would give Sasha an even bigger PCS advantage than what he got, but it's quite rare to see the country's #1, who went to Europeans and medalled at senior Nationals, receive lower PCS than the #2. And said #1 also had the cleaner jumps. If competing in seniors was such a dealbreaker, this wouldn't have happened).
Kim Jin Seo also competed in seniors, and he didn't get particularly generous marks.
I do think there should be some kind of parametres to prevent Jr-Sr hopping at any time, but in the case of Shoma's marks, I think it's just how the judges score him. Has nothing to do with the "come from seniors" marks.