>Does this have relation to China announcing they will build several thousand nuclear warheads in the coming years?

These are numbers from the Pentagon, not from China. They went from 200 warheads to 400 and the Pentagon said "If they keep going at this pace for more than another decade, they will be at 1,500 warheads!!"

It's a nonsense idea.

Think about why the Pentagon might want the American people to be scared of a rising Chinese army. What benefits could they get from pushing the idea of a warhead gap?