Getting passed up while loading into mission

[(XBOX)Un Fetty Wap]

With the original xbox one, the loading time is slower than pc by a few minutes. For some odd reason, the way the matchmaking is set up is a "first come first serve" where they are literally throwing 5, 6, I have seen up to 7 players joining a single game at once. Just open up your chat to see the players in your game, and you will see more than 4 while joining a "hot" game like a sortie or an alert. Once I am in a squad of 4 and loading in, if I see a 5th join in or more, I am guaranteed to be booted back to the menu for the reason of "the game session is already full". It should have been full with me being the 4th. I have never actually seen a game operate this way before, but I also have never played a cross platform game where other platforms can outperform the one you are on.