Do you remember before the prequels? The original Trilogy had certainly set us up to expect certain things from the backstory of Obi Wan and Anakin. The Prequels came and thrashed every idea I had about their relationship.
But just like how Star Wars Rebels is acting like a throwback to many old concepts, like Ralph McQuarrie art... I believe they are also acting as a throwback to how that relationship between Obi Wan and Anakin SHOULD have been. Reflecting that relationship in Kanan and Ezra.
Statements like Obi Wan saying :
"When I first met him he was already a great pilot" - goes back to episode 1, Ezra is piloting the speeder when Kanan encounters him. And it's actually Kanan meeting Ezra, not some other guy meeting ezra and later saying "Oh btw, kanan meet ezra, ezre meet kanan. "
"I took it upon myself to train him" - Kanan wasn't forced to train Ezra by some dying master.... Kanan did this on his own.
" and a good friend" - You TRULY get the feeling that Ezra and Kanan are good friends now. Their teamwork is simply amazing. Their relationship is freaking awesome.... and IF Ezra ends up turning to the dark side at some point, it's going to be that much more heartbreaking.
This is Disney, fixing the prequels, in my mind.