After 27.d6 Bxd6 28.Rxe8+ Qxe8 29.Qxd6 Qd7 the end result may appear to be the same, but on closer inspection this variation end game results in black down 2 pawns and with the knight versus the rook; in the actual game black is down 3 pawns and has the DSB vs the Rook. White's f-g-h pawns are all on dark squares and black's DSB is impotent.

You have to take advantage of every little advantage, even if it seems to be slight. In your line, you have to deal with the knight hopping all over the board, and yes, although you will most likely win, the clarity of the actual game is a slight nuance which translates into a clearer win.