Well it's obviously not a "strategy" to lose territory, not directly, but if your supply lines are overstretched then it makes sense to yield some territory to bolster your supplies elsewhere. Seeing as we're talking about an area roughly equivalent to Hampshire (pulled out of my arse), it's not out of the question that Russia felt yielding such a small amount of territory is a viable option.

I'm just spitballing here. I have no idea what's happening on the ground, why the Russians are losing territory, I don't know how significant that territory is (cities or fields?), and that's because I have no source of reliable information. It's a propaganda war too, and both sides are playing this game. How do you know what to believe?