What is a sacrifice?
A sacrifice means you lose X on purpose to gain Y (something better). If you don't gain anything back, it'd be a blunder or an unsound sacrifice. The example in the OP is definitely a sacrifice, albeit a simple one - you lose the Q to gain a checkmate.
I wouldn't call the OP mate a sacrifice, I'd just call it a forced mate.
But it doesn't really matter what we call it. You can call it a sacrifice.
The line between a sac and a pseudo-sac is hard to draw. Is it only a sacrifice if it's unsound? That seems rather restrictive. In common usage, it's a pseudo-sac if there is an immediate and obvious tactical follow-up, and called a sacrifice if the follow-up is harder to find.
Here is Troinov vs Popov, for example. Even though the win is forced and amenable to calculation, I would still call this a sacrifice, not a pseudo-sac.
I understand that sacrifice means trading down or giving up material without taking any material in return.
However in this position -