[SideburnsOfDoom]

> although saying the accusations are "nonsense, utterly ridiculous and should be ignored" isn't strictly speaking the same as saying that they're untrue.

I would think that "nonsense" implies "untrue". I.e. it is "The subset of untruths that also are logically inconsistent"

We are splitting hairs of the fine parsing of the wording from GCHQ, when words of any kind are highly unusual.