What if the coach is using this pick up player as a tryout for that player? Coach: Hey kid I really like what you have to offer our team and would like to offer you a spot. Player: Coach I'd like to play with the team in a tourney to see if it would be a good fit.
Player plays in the tourney and realizes that the parents and players are not receptive to her presence. Player moves on and the team loses the chance to bring on a ringer.
That happens, and it's a reasonable move if there's a need at a particular position, or the roster is small and needs more depth. IF there's a legitimate need, then a player in that scenario is likely to be welcomed. If she's "trying out" with a team of 12+ for that weekend, then maybe not.