Lea being in a coat simply means he was in a coat when he lost his heart, which isn't hard to believe given you know he revived in the secret lab meaning he was involved with apprentices before hand. Roxas's outfit is kind of completely irrelevant? The outfit of the nobody doesn't matter, it's formed from memories like rest of their appearance. The outfit for the original does matter because when they revive that is the outfit they will revive in. That is why Vexen dies in an org cloak but revives in his Radiant Garden garb because that is what he wore when he lost his heart.
It's blatantly obvious they're just reusing assets so they don't have to make any new designs. As they say in my country, no use in searching for the cat's fifth leg.