Okay, this is likely my last post on this line. After

1.d4 Nf6 2.c4 g6 3.Nc3 d5 4.cd Nxd5 5.g3 Bg7 6.Bg2 Nb6 7.Nf3 Nc6 8.e3 0-0 9.0-0 Re8 10.Re1 a5 11.Qe2 Be6 12.Nd2 Nb4 13.Rd1 c6 14.a3 N4d5 15. Nce4 Bf5 16. Nc5 e5! 17. dxe5 Qe7 18. Nd3 Bxd3 19. Qxd3 Qxe5

What should White’s next goal be? Two ideas come to mind:  b3 followed by Bb2 or Nd2-e4-c5. Even together they do not amount to a forced win, but the idea is to increase the pressure on Black.  The right way to start seems to be

20. Rb1

[This move seems important even if you wish to start with the second idea. Here is one possible (completely unforced) line

20. Ne4 Nf6 (preventing 21. Nc5) 21. Nxf6 Bxf6 22. Qb3. 

Now it seems White may be getting somewhere, pressuring the queenside, and hoping to play Bd2-c3 at some point. However, Black can exploit White's lack of development.

22…Rad8! 23. Rxd8 Rxd8 24. Qxb6 Rd1+ 25. Bf1 Qd5 26. Qxb7 Qc4 27. Qc8+ Kh7 28. Qh3. 

White is not being mated, but he can barely move a piece, and Black, a piece down, cannot possibly lose unless he overreaches. It is hard for Black to make much progress, though, so the most likely outcome seems to be a draw. 
However, if White’s rook had been on b1, he could have avoided all this by playing 23. Bd2! with a winning position!]

Now, after 20 Rb1, 20 …a4 makes sense, and White can proceed with Ne4.  A sample line is

20 Rb1 a4 21. Ne4 Nd7 (this is not forced, but makes sense) 22. Bd2 Red8 23. Qc2 Qe7 (continuing to prevent Nc5)

and now White can even try 24. Nc3 with the idea of trading down to an endgame with Black having weak queenside pawns, all on light squares, and White having the strong bishop on g2. It’s not much, but it allows White to play on without fear of losing, and causes Black to work a bit more before earning his draw. 

That position still seems to be promising for Black due to the dynamic potential of the minor pieces, something that seems to be a major factor in preventing White from seeking an advantage in this line.

Another Avrukh's line in Gruenfeld goes like this:

And here my opponent in a recent correspondence game of mine played 15....Qc4!? obviously trying to equalize by exchanging the queens. This move is not mentioned by Avrukh. My game continued:  16.Qxc4 Nxc4 17.Nd5 Re8 18.Bf4 Nb2 19.Rd2 Nc4 20.Rc2 b5 21.Ne3 Nb6 22.Rd1 Rb8 and black soon achieved what they wanted.. 1/2 

I am a newcomer here, and perhaps this question has already been asked and answered, and, if so, I apologize, but I am stuck. 

Avrukh’s main line in the fianchetto grunfeld was busted – 
1.      d4 Nf6 2. c4 g6 3. g3 Bg7 4. Bg2 d5 5. cxd5 Nxd5 6. Nf3 Nb6 7. Nc3 Nc6 8. e3 0-0 9. 0-0 Re8 10. Re1 a5 11. Qe2 Be6 12. Rd1 Bc4 13. Qc2 Nb4 14. Qb1 

(White’s queen has been pushed around, and ends up on b1, while Black’s pieces move to seemingly aggressive squares. Avrukh’s  idea is that White will begin to push Black back with a3, b3, e4, f4 and emerge with a better position, and provides some compelling lines to show how that might happen. However, it is obvious that if Black finds a way to take advantage of his “temporary” activity, the assessment could turn completely, so …) 14…e5!!!  A wonderful move first played in McNab-Djukic, Khanty-Mansiysk 2010, which leaves White in a real mess (e.g. 15. a3 exd4 16. axb4 dxc3). In response, White now usually plays 12. Nd2 (with the obvious goal of preventing …Bc4), but the line suggested in Delchev& Agrest:

12. Nd2 Nb4 13. Rd1 c6 14. a3 N4d5 

seems to lead to an easy equality.  (I have searched unsuccessfully for a way for White to keep fighting for an advantage in this position.) 
However, even after these ideas became well known, the “big boys” are playing 11…a4, a natural move gaining space and making White’s move b3, a central idea in this line, more double-edged. Here, White can still fight for a small advantage in a few ways, including Wesley So’s fantastic
12 Rd1 Be6 13. d5 !
The question is - Why is Black avoiding 11…Be6 ? It looks to me to be a complete solution.  Can anyone help? How does White fight for an advantage here?