This was apparently announced at E3 and just fell through the cracks. I'd imagine most players were likely unaware that this was a new feature for this port of RE6 (Only other options is on PC with Mods). It also hasn't been used as a selling point for some reason, even though it's a switch port exclusive. In the video below Chris is wearing his EX 1 outfit in the opening mission of his campaign.
This is a nice little addition for fans of the game, as even back in 2012 it was an oddity that you couldn't use the costumes in the campaign without modification.
Here's are all of the costumes in the game
This is a nice little addition for fans of the game, as even back in 2012 it was an oddity that you couldn't use the costumes in the campaign without modification.
Here's are all of the costumes in the game