Ulhumbrus: If 11 d4 compels Black to concede an advantage in space to White by 11..exd4 this suggests that the move counts as a threat.
The move 11 d4 comes with tempo as it attacks the bishop on b6.
This suggests saving a tempo by delaying some other move earlier. However on eg 9...Ne7 instead of 9...Be6 10 d4 Black still lacks time for ...Ng6 and on 9...Bb6 10 d4 Black lacks time to play 10...Ne7. Or earlier on 6...Bb6 7 d4 Black can't play ...Ne7.
However on d4 Black may have the option of ...exd4 and ...d5 with White's bishop still on c4 as in the classic game Tarrasch vs Alekhine, 1925
This suggests 8...Bb6 eg 9 d4 ed 10 cd d5 with White's king's bishop still on c4.
If 13...d5 risks making the c pawn backward one alternative is 13...c6
19 a4!! begins the plan of playing the queen's bishop to a3 and removing Black's knight by Bxe7 so that the move Qd3 cannot be answered by ...Bf5.
This suggests that the pawn advance a4 is an attack upon the square h7, not immediately and not directly but more distantly and more indirectly.
Moreover the move Ba3 will pin the knight on e7 so that it can't support the move ...Bf5 unless Black spends a move on unpinning it by ...Rfe8 and the capture Bxe7 can remove it even then.
This suggests that instead of 19...Qd7 19...Bf5 is necessary, to answer
White's attack on h7 before the move Ba3 can pin the N on e7.