They have endured the launch of the game. They will get to play a game where they will not have to experience all of what we have had to. What will they miss out on? They will get a far better, and closer to finished product than what we started with. Guns in primitive. Under map tame killing. Duplication glitches. The list goes on and on. Lots of things that they will never have to endure and recover from.
It's not like we had any special events (though we were supposed to) except for the Turkey, and even it started out as a disaster as WAY over-powered Turkeys decimated bases.
Hard to compare a Rex to a Giga. One is almost phased out due to the other. And as you said, the Manticore outfits.
Regardless, it's still a slap in the face. I know there is tons to come from the game itself, but instead of offering someone something exclusive for buying the game, WHICH XBOX USERS RECEIVED NOTHING I may add, how about offering this to all players as a celebration for the game and community in embracing the PS4 console and players.
Also, I saw someone else mention buying a PS4. I will NOT buy an entirely different console just to get a skin on this game. That's a little overboard. 3000 hours logged in this game, and even as dedicated of a player as I am, the skin is not worth buying an entirely new console to me.