Yea, I actually noticed that the 1st time I saw my cousin playing him-it looks like it ties into all of the "chaser/Xeanhort's memory"-theories that have been bouncing back & forth across the web. Then as to "why/how" he had gotten the armor, it's (I'm guessing) out of a few reasons:
-He got it because he fought with a combonation of the recently fallen Org. members when he was on the throne
-He just MIGHT be a rumoured chaser from the teaser for KH-3
-The armor mixes into a piece of storyline that we have YET to discover
Or then again Tetsuya might have been just screwing with us to make us THINK that we know what it means, when in reality he meant it to be just the opposite.