Fritz's King's Indian is hard to crack!!

Rhoney - Fritz 7


Here's the opening -- I went out of book on move 12. but I think fritz
has a game with this move played in its database.

96MB, Fritz7.ctg, Pavilion
 1.Nf3 Nf6 2.d4 g6 3.c4 Bg7 4.g3 0-0 5.Bg2 d6 6.0-0 Nbd7 7.Nc3 e5 8.e4
c6 9.h3 Qb6 10.Re1 exd4 11.Nxd4 Ne8 12.Nde2 Ne5 13.b3 f5 14.Be3 Qa5
15.Rc1!?

offering a positional pawn sac. to throw of eval. function 15...fxe4
16.Nxe4 Qxa2 17.Bd4 Qa5 18.Ra1 Qd8 19.f4 Nf7  20.N2c3 a5! 21.Ra2 White
looks clearly better but Black's position is solid. What am I missing?