To elaborate, the two links you offered do not contradict, they merely offer detail, and of two different types.
Thus: My link #1 is of the Tensor fascia lata. Note the middle name is fascia? My link for that one says “Helps stabilize and steady the hip and knee joints by putting tension (hence Tensor) on the iliotibial band of fascia.” (note fascia again?) Your link says inserts in the “Iliotibial tract”. It does not specify what they mean by “tract”.
My Triceps link says it inserts on the ulna and “fascia of forearm”. Your link, however, is not an academic link but is ultimately from some business site, so I can forgive them for their lack of completeness. The Loyola U. site mentions something about a “posterior capsule” insertion, but does not mention forearm muscle fascia. You do make a good point, as did frogs, of consulting many sources and going with the majority. Books published and cadavers dissected are both however subject to statistical sampling error.