Spanish game

It looks like it should transpose. White cannot stop black from playing b5 at any point after a6 has been played, so he doesn't really have a say in the matter if he wants to play the main lines. There is one independant line with an early b5 for black that I know of. After 5.Bb3 black plays 5...Na5 instead and goes for the bishop pair. This is called the norwegian variation and I think it looks better for white. Just something to look into...
So why i have never seen any game of grandmaster whis this move order? :) i just dont get it, but i also think that it should transpose, i know about Na5 variation but i asked about this because i want to play main lines more often (delayed exchange variation is very frequent, and i dont like playing it)

Alright so I just looked in my database and the most common move seems to be 5...Na5, although 5...Nf6 appears to just transpose back to the mainlines in most of the games. 6.0-0 is usually played, followed by 6...Be7. Then of course 7.Re1 is the mainline, but white can also try 7.d4. This probably doesn't lead to a better position than the mainline, but it is worth looking into. Statistically white seems to be doing quite well here though.