I can just imagine a younger John wanting no input on his costumes at all

Yup. No interest in that part.

Years ago, when John was a teenager, he tried to get his mom to "fix" his costume after the fact. He knew it wasn't quite right, but was unable to articulate why. They went through a dozen variations until he gave up and lied, "This one's great!" just to get her to stop.

it must have been disconcerting for Rodney to have his worlds collide

Rodney still feeling smug that Radek's been carrying a torch all these years. Yeah, Rodney, that's why you're the one who calls him all the time.