Strange. The obvious likelihood is that the soldiers were actually killed during clandestine activities in Ukraine, and these dirty deaths are now being laundered by means of "accidents" in legit places. We have seen a number of these already with US forces and other NATO countries.
However, now that Trump is in power, I wonder that they don't take this opportunity to release the fact that Biden had been doing this, but Trump was now ending this activity immediately. It's not like Russia doesn't know about this.
However, even if we know that Russia knows, Trump and his team may think it is it too damaging to acknowledge this activity openly. Even if it was conducted under Biden and (if) it is being ended now under Trump, acknowledging it openly might give Russia some kind of additional diplomatic advantage in the coming negotiations. For that matter, Trump may still be aggressively placing clandestine US forces in Ukraine, even as he says he's trying to end the war.