Yeah, I think that's an interesting theory. But to be honest, taking the prequels into account (which not everybody does) Obi-Wan's explanation serves very little purpose. It was really just to bring us as the audience up to speed on what happened, but we already know that from Ep. III.

Plus if he had told Luke this in the first place, would Luke have gone with him? Would he have tried to reason with Vader and be killed, thus ending their last hope at restoring balance? If I were Obi-Wan, I wouldn't have told him till he was ready, and unfortunately he found out from Vader himself long before that time.

I've been discussing this a bit in some other forums, but I like to think that a big part of how Anakin turned out has to be attributed directly to Obi-Wan. to me he is just as responsible for Anakin's turn to the dark side as Padme is (both indirectly and without intention, obviously.) With a stricter master, things would've turned out quite differently, but it was his fate to end up with Obi-Wan, a young and brash Jedi who was not ready for a Padawan. It was also destiny that Obi-Wan was trained by Qui-Gnon, thus promoting his cavalier and sometimes disobedient attitude. I gotta give George credit, he really thought that through, and I can't think it was coincidece that all those pieces fell into play.

Sorry, off topic.