Up to this point, the game has followed book lines. Black diverges here; the Black KB is more often placed on either e7 or c5. This placement on d6 will expose it to risk, if Black is not alert.
9. e4 Bf5g4
This move looks inconsistent, as 5. ... h6 strongly indicated that Black intended to retreat the B to h7.
10. h3 Bg4h5
Black has now moved this B 3 times in the first 10 moves. Such a loss of tempo is possibly not critical in a slow game such as the Reti, provided Black gets his B onto a good diagonal.
11. Qd1e1
Not only unpinning the N on f3, but threating to advance the e-pawn, forking the B on d6 and N on f6. See note to Black's 8th move ... Bd6.
11... O-O
?? A careless automatic developing move. 11. ... Bc7 was unpleasant but imperative.
12. e5 Bh5xf3
That makes 4 moves with this B in the first 12, a serious loss of tempo.
13. Nd2xf3 Nd7xe5
This exchange is not forced and tends to favour White.