Not crazy insanely rude at all! Dude is left all alone for days while they are having fun training as a team in tandem with the girls to get better but NOBODY thinks of telling him. That makes sense and is not wasting his time at all while making him feel bad!
But he only went out of his way to compile all that data and take the lead that nobody else wanted. Why would he be allowed to have fun with them and improve massively next to them, hah!
How the hell....why wouldn't they explain that too them? This doesn't feel like they have an emotional reason why they didn't tell them. They just have...no reason. and it's not like it's going "Yeah they're dumb teenagers." it's framed as a teamwork momment??
That was kind of a neutral-dick move the other players did (neutral because the results balanced out the negativity Souta almost end up concluding things with). But I guess it is the best way for the others to learn and develop themselves more since they are not as intuitive and as driven as Souta in the first place; and it is also nice of them to recognize they are only as motivated as they are now because of Souta
I don't think it's all that deep you guys, this is a bit of a rest chapter mixed with the author trying to show that the team still trust their captain. Plus it's showing how because of him they continue to become more and more united.
It does suck they didn't invite him though but I guess for the sake of showing those three aspects it needed some low-stakes conflict, author just picked a bad way to do it lol.