No it isn't. It is the soundest piece of advice in this whole thread.
It would be the height of arrogance and irresponsibility to show up with a Rebel and a kit lens and try to learn on the job. Nothing wrong with the Rebel mind you..
It is somebody's memories he would be playing with. He goes through a set of snaps, the result is lousy and he goes 'Oh-oh, I better give you your advance back...'...??
What are the newlyweds gonna do? Get married again?
He should train himself as a photographer, he should apprentice as a wedding photographer and when he's good and ready, he can hang his shingle. Otherwise, it borders fraud...
Getting into photography classes is a quick way of getting the basics. You can do it by yourself, but it will take time and inclination (to learn, not to photgraph...).
I like shooting portraits, I like candids, I shoot my wife's group for their pleasure and mine. I would not assume the responsibility to cover a wedding, a graduation or a confirmation. I am a competent amateur, but not a professional. I cannot assume the responsibility of a pro.