I think you're just getting confused over the translation here. Yes he does say that Rasengan is an A rank jutsu or whatever. But that's just the class of jutsu just like bunshin or kawarimi are probably D rank or so. If you can do a bunshin really well it doesn't mean that it's suddenly become an A rank technique or anything. There are three stages to learning Rasengan as far as we know in the ANIME if there are any more then I don't wanna know yet.