@DVRazor: Well, it's a more quiet move than you would typically expect, certainly.
Having said that, it has a concrete threat (Rd7, winning the queen because of Rh7#) and basically wins the exchange because allowing the other threats is much worse for black.
So, Rd7 must be stopped.
Bc8 allows the funny (and quite tactical) Rc7 Rxg4+ Bxg4 Rxg4+ Kh2! (after Qxg4 Qxc7 white is still doing well, but not completely winning as in the main line), and now if Rxf4, just Rxe7 and white picks up a lot of material because Bxe6 is forced. If instead of Rxf4 black tries Rh4+, then Kg3! makes things worse, because now after Rxf4 Rxe7 Bxe6, white can check on the back rank and pick up the rook with mate to follow shortly.
If instead black tries to stop it with Rd8, then after Rxd8+ Qxd8 Rc7, black is toast because his check doesn't lead anywhere (Qd1+ Kf2! and there are no good checks).
It definitely isn't the stereotypical tactics puzzle where your first move is a check or sacrifice, but sometimes quiet moves make threats and force wins too.
I'd definitely still call that a tactic (again, in the simplest description of the puzzle, you make a threat that forces the win of material), but I may be a bit biased because my favorite tactics trainer is chess.emrald.net, where such puzzles are not at all unusual (in fact, they also include puzzles where you have an only move to draw, not to win).
As with so many things, we just end up at the fact that different people want or expect different things, so it'll always look weird to somebody :)
Having said that, it has a concrete threat (Rd7, winning the queen because of Rh7#) and basically wins the exchange because allowing the other threats is much worse for black.
So, Rd7 must be stopped.
Bc8 allows the funny (and quite tactical) Rc7 Rxg4+ Bxg4 Rxg4+ Kh2! (after Qxg4 Qxc7 white is still doing well, but not completely winning as in the main line), and now if Rxf4, just Rxe7 and white picks up a lot of material because Bxe6 is forced. If instead of Rxf4 black tries Rh4+, then Kg3! makes things worse, because now after Rxf4 Rxe7 Bxe6, white can check on the back rank and pick up the rook with mate to follow shortly.
If instead black tries to stop it with Rd8, then after Rxd8+ Qxd8 Rc7, black is toast because his check doesn't lead anywhere (Qd1+ Kf2! and there are no good checks).
It definitely isn't the stereotypical tactics puzzle where your first move is a check or sacrifice, but sometimes quiet moves make threats and force wins too.
I'd definitely still call that a tactic (again, in the simplest description of the puzzle, you make a threat that forces the win of material), but I may be a bit biased because my favorite tactics trainer is chess.emrald.net, where such puzzles are not at all unusual (in fact, they also include puzzles where you have an only move to draw, not to win).
As with so many things, we just end up at the fact that different people want or expect different things, so it'll always look weird to somebody :)