Since the question is apparently about the letter ɧ and not a sound of a specific dialect of a language, we have to answer the question first according to some system of standards. It is part of the IPA: to get an authoritative view of what the thing sounds like, go to the International Phonetic Association (webpage) and see what the experts say. Look for ɧ here and play the 4 recordings. What the experts produce seems to satisfactorily fall into the category of "sibilant". You can also put your faith in Wiki and listen to a performance of ɧ, which is not a sibilant. I would be inclined to dismiss Wiki contributions, but the speaker's audio chart is linked in the IPA web page, which may be accidental, or it may be an official sanction. By a majority vote, I'd say that the IPA use is "a sibilant".
However, I have heard a bunch of Swedish people speaking their language and have notes them using a funny quasi-rounded fronted [x] in words like skit, sju, skyr, sjö. You can hear samples on Forvo, which sound very much like the minority pronunciation on the Wiki page. I believe that the producer of the minority pronunciation is a speaker of Swedish, therefore his pronunciation sounds like it does in Swedish. This is similar to the problem that expert renditions of [ħ,ʕ] do not sound like those sounds in Arabic. It's not that the experts are wrong, it's that IPA is a standard against which specific language sounds are measured, so Arabic "ʕ" is most like IPA [ʕ] – IPA [ʕ] is not defined in terms of Arabic, or Swedish, or whatever language may be generally thought to have a certain sound.
The much deeper question is, what is the history of ɧ in the IPA. The letter seems to have been added to the 1947 chart, judging from the IPA's historical chart page. Associated with any symbol should be some phonetic description, in 1947 described simply as combination of ʃ and x. Auditory standards were established in (a few) classes, since the internet was not functioning at the time. One could read Maître Phonétique in the surrounding years to see what discussion there is that leads to the current system: it is doubtful that there are any living participants from the era that could testify on the matter.