That’s a very poor showing for a hydrogen weapon...but it does fit the profile of a boosted EMP design.
When I consider threat I look at direct impact on my grandchildren. As I live in BF Kentucky my nightmare scenario is an EMP attack. Even though we are dealing with a maniac I think he realizes his best bang for the buck would be the EMP attack. He must also realize he has one shot as North Korea would immediately be turned into a smoking slag heap.
Yup, ‘boosted’ fission device at best.
Fusion devices are opened ended on maximum yield. The important thing is weight. Perhaps this weapon is at the max deliverable weight for their missiles.