I dunno about that. The fizzle part may be true, but I believe the fissionable material used was uranium.
Folks who know more than I about testing say that the test was likely to determine whether the first stage of a two stage detonation would work, and this uses uranium to ignite the reaction of a plutonium second stage, and thereby create a hydrogen bomb. the plutonium comes from spent nuke fuel and has a higher yield. You can't make a very small plutonium bomb without big-time knowledge and processes. The yield would have been measurably higher.
This is why Kinny had the uranium enrichment thing going in secret at the time of Clinton's bad deal, and also why Iran is enriching. It takes the two materials to tango, as I understand it, and play with the big boys.
Kinny=Kimmy
Who is to say that Kim doesn't have that at his disposal? Not everyone starts from scratch on these things. There are plenty of other countries that would love the data from such a test but for political reasons cannot conduct one on their own. Even Kim's nearby benefactors could have ben involved.
Consider, too, that the first test could have been a smashing success (npi) and that further tests are unnecessary. Why not be magnaminous in that case and play the "look, he apologized ... what a guy!" game the press and Europe seems to lap up?