It's the kind of absurd demand made when people have no intention of negotiating in good faith.
of course its inclusion is a sop to Poland:
"...In July 2007, Russian First Deputy Prime Minister Sergei Ivanov declared that if US-controlled missile defence systems were deployed in Poland, then nuclear weapons might be deployed in Kaliningrad. On November 5, 2008, Russian leader Dmitry Medvedev said that installing missiles in Kaliningrad was almost a certainty. These plans were suspended, however, in January 2009."
It says effectively: " Well, em... we want to put nuclear missiles in Poland and point them at you, but Kaliningrad is making things difficult cos you might point some back...and we couldnt stop them. So we want your military out of there. "
-The thinking is so transparent US diplomats cant really believe this will be taken seriously, because it won't be: Its on the level of a joke.
What's worrying is it might not be and that the US Military Industrial elite might have lost touch with reality to such an extent that they think it really is a serious proposal.