Notice the game being played. The troops aren't supposed to be there on a permanent basis so they get around it by rotating the troops every six months.
The US does this all the time. They'll list a base as having say... 500 personnel but then they might have 2000 more there on a more-or-less permanent basis but can avoid the designation by having them on a rotation. It's an accounting trick.
Of course a war game with a simulated nuclear attack involves drilling for a counter-attack. Moscow knows this all too well. It's kind of like missile 'defense'. Part of the defense is striking and taking out the other side's weapons. George Bush already demonstrated what pre-emptive 'defense' looks like in 2003.
Also the fact that they're paying lip-service to a 1997 NATO-Russia agreement makes a mockery of the original US promises made under Reagan and Bush I. They had assured Russia that NATO would not advance to the east. It was on that basis that Gorbachev allowed not only German reunification but the newly united Germany to join NATO. That was an explicit break with everything Russia's military and strategic planning in the European theatre had been about since 1945. The great fear has always been a unified Germany. Whether that Germany was under the power of another authority really didn't matter. A united Germany at least according to the Russian read of history would (and will) inevitably lead to war with Russia.
That reality is looking all too ominous a quarter century after the end of the Cold War.