In its top five lines it has White castling Queenside but more often Kingside, depending. Black castles Kingside in four of the lines but in one line Black doesn't castle. It doesn't have Black castling Queenside in this setup. Often in the Scandinavian Black castles Queenside or has a choice between Kingside or Queenside, but in this particular setup SF doesn't seem to approve Queenside castling for Black and it's rather obvious why --- Black's f7 pawn needs defending.
A reason why I play the Tarrasch Defense against the QG is because my King rarely if ever comes under attack. The same can't be said for the Scandinavian (I don't think a defense against 1 e4 exists in which Black's King is as safe as in the Tarrasch Defense) and I knew when I played ...0-0 he was likely going to play 0-0-0 (and yep, he did) to come after my King, but it didn't look all that avoidable to me so I thought ok game on. That he is an FM had me extra concerned for my King.
#66, just finished chapter 5. that section is next. I think it's possible he played 9.Bd3 simply out of principle since blacks bishop is not on f5. yeah, c5 seemed a little early. after Na6, did Sf suggest 0-0 or 0-0-0 for black? I don't have a computer. I'm just curious.