I'm not an expert on nuclear weapons. It's simply that anything with a letter fits the template. It's also just trying to make light of what is a very serious situation.
It's a great meme, I upvoted it :) I've been wondering about the whole "apparently not atomic hydrogen bomb" while watching the news. Socrates said it has to do with the difference between fission and fusion.
I think experts are casting doubt on the claim due to lack of evidence ie the size of the explosion etc. North Korea are just reminding the world they are still there.