And the non-virtue of being infeasible.
With passive radar systems capable of alerting to stealth aircraft passage now becoming increasingly available [likely first tested in the Balkans] , once the Russians detected the incursion by B-2s, they would know who to blame, and the SS-18s would fly.
Just because you are unable to figure a way to execute a first strike with bombers doesn't mean that others aren't. The USSR ran an exercise in 1984 that led off with a US first strike carried out with B-52s, followed by an ICBM strike. The defenders got their asses kicked--had it been a real war, the USSR would not have gotten a shot off.
The USSR changed . . . nothing. No significant policy changes, no changes in procurement, no changes in doctrine or training . . . the military wished the exercise into the memory hole. Really major embarrassments tend to do that in peacetime.
Also, the Russian air defense system is much hyped, but its actual history points to its combat performance not matching the hype. When one off-course Korean airliner can cause a comedy of errors that would've been laughable if it hadn't killed 269 people, there is little reason to assume that it would work under anything but the most trivial attack.