1♦-1♠-2♥ is forcing, in sayc and 2/1, and most of the natural system, I believe. Precision is different. 1D opening limits the hand to 15hcp (assuming 1♣=16+). Though 1D opening is also limited (to 20 or 21), it has a much broader range. A reverse hand opposite a hand that can respond, game is very close. Even if responder has dead minimum, game is still very possible. I know, if you hold ♠QJxxxx, ♥xx, ♦xx, ♣Jxx, and responded 1S over pd's 1D opening, game is not likely when pd reverses to 2H. But hey, pd may have 3 ♠ and is false-reversing ♥ to wait for your clarification.