I don't see how the reasoning of you preordered from Gamestop and not Best Buy or Walmart means you don't get a skin without paying a premium later on down the line differs from there being a few skins you only get from supporting their mobile game.
Because anyone can pre-order. You are comparing apples to oranges.
Any person can go and pre-order something. The amount of people being "left in the dark" is very very few, and they are only left in the dark due to stubborness or lack of any game store within reasonable distance(understandble).
With the iOs game, you have to buy an iphone/ipad. Which is no cheap expense. Which means the amount of people who don't have one, is far greater of a percentage. Meaning the people left in the dark, are the majority.
Also, pre-ordering takes 10 min. of your time tops. Playing the iOs game takes 40 hours of grinding to achieve everything.
Besides, EVERY game has pre-order bonuses. This is nothing rare. Making people pay because they don't have an expensive device, and tons of hours to dedicate, isn't common. Apples and oranges...
That's the difference. The outfits will likely be unlockable. It makes sense.