Fairly clear what's going on to me. He's basically daring Kroenke to do something about him.
He'd take Arsenal if it came up, but he knows it's next to impossible. Therefore, he's trying to game his way into offloading his shares for the maximum possible price.
By saying he's not interested in selling to Kroenke, he's engineered a situation where he's invited other bidders for his stock, or Kroenke will have to pay big to get them.
It's smart. Everything Usmanov has done is very, very smart. And I have very few doubts that his end goal here is Everton - too many actions and too many words have pointed in that direction for it to be otherwise.