You keep casually lumping in USNTDP and Green Bay together as one in the same, I'm not sure. Yes, he went to the USDP Camp and was cut from the final roster, nobody is disputing that. That doesn't mean he wasn't good enough to make Green Bay in the USHL this season. You are saying "there was an intention not to stay at Shattuck"... where are you getting this information? You are stating that he certainly would have chosen the Green Bay Gamblers over Shattucks-St Mary's if they had wanted him, but this is a completely baseless statement. These are minors we're discussing, they aren't solely seeking out the best available league to play in at all costs because they are not professionals. They have very important and real life considerations involved that play a role in their decisionmaking.
Shattucks is an elite academic prep school that we know he chose to attend by enrolling when he did, Green Bay is a USHL team that drafted him. Kids can play at a prep school and be prepared for college hockey and be drafted in the NHL (some have even been 1st round picks) and SSM is no different in this respect from some of the other prep schools. I don't know how you can completely disregard the very real (and in my opinion, more likely) scenario that the hockey difference between USHL and SSM this season wasn't high enough to overcome the academic and overall lifestyle (friends, familiarity) difference that SSM provides.
There is a pretty clear indicator when a kid is not good enough to play for the USHL team holding his rights. It's when they are playing in the NAHL and getting called up for a series here and there with the USHL squad if someone is injured or what not. That would mean they've made the choice to jump to Junior Hockey, and if they're playing NAHL games instead of USHL games, it's pretty easy to infer why. This is not the case with Park, who is on a different path by playing a prep school that is still a feeder to NCAA Hockey, like those junior leagues.
As far as the Celebrini/Eisermann stuff, nobody is still debating that with you, so there is no need to continue to beat that dead horse.