The current Baltic NATO states and Norway are much easier to defend having control over the Baltic Sea, plus Finland has a considerably strong military that now joins to strengthen NATO, so it should be a win-win for the both sides.
NATO has never publicly committed to a NFU policy because that would weaken their hand on the political stage but in practice they seem to be following that line. It's a smart way to position themselves, and other nuclear capable entities have done the same.
NATO no longer faces this threat, but the policy remains.
Of course, the problem is that Putin has a very expansive idea of "what threatens Russia"...