It's not about whether they are serious about nukes or not but about giving due respect to the threat. Ignorantly presuming that they are bluffing or Russia's nukes are outdated (which some Western media is espousing) is more escalation. In one year the last nuclear treaty, which obliged each side to inform the other about nuclear movements, is done and dusted leaving a trust gap. If communication channels are going to break down at this pace then more trust gaps will appear.