I can't say that I agree. The quoted language--"It simply does not make any scientific sense to create a new threat just to develop new countermeasures against it"--is too cute. It assumes that noone else can accomplish the same thing as the researchers did. But if the researchers can do it, so can NK, China and Iran. Don't you think it would be a good idea to understand the genome of this killer for countermeasures?
I have no doubt a few of the more developed totalitarian regimes could duplicate this kind of research. However, unless a western nation supplied the tissue samples, i.e. knew precisely where to exhume a soldier buried in permafrost, I find it somewhat unlikely that North Korea would embark on finding 1918 flu to work with. Ebola or something equally heinous perhaps would be more readily exploited. The choice of weaponizing Spanish Flu just seems strange for "terrorists" but does sound more plausible for a Western government to choose. Not to deny the possibility that OBL or someone may not see the usefulness of weaponized 1918 flu, but we shouldn't do the groundwork for him.