For sure white could and probably should have played Na3 earlier than he did but playing cxd4 doesn’t somehow magically stop the onslaught
Which onslaught are you dreaming of? Black has a clear advantage after 9...cxd4, dude.
10.Nb5 fails to Qf5!, 10.Nxd4 loses a pawn, while 10.cxd4 0-0 is a textbook example about how white should not treat his IQP: Two pieces (Na3, Bf4) stupidly placed.
For sure white could and probably should have played Na3 earlier than he did but playing cxd4 doesn’t somehow magically stop the onslaught