>with ~31% originating from Europe (East and West combined).
I think the parent comment was referring to the idea that the overwhelmingy majority of those "Europeans" we're rather people of MENA/Turkish immigrant background, not "ethnically" European.
>>spider+(OP)
Even if that's what the parent comment was implying it still wouldn't be correct; much more than 5% of ISIS' fighters were "crazies" from "Indonesia, Chechnya, etc".