Evolution is too big a thing to be a fact. Facts are small things and relatively meaningless. Interpretations are large things and full of meaning.
For examlple take these statements about reality:
World War 2 began in 1939 - is a fact.
World War 2 was a result of the failed policy of appeasement - is an interpretation.
Evolution is much closer to the second statement in terms of interpretative scope. The more focused a statement the more closely it resembles as fact. The wider in scope, and full of meaning, the more it resembles an interpretation rather than a fact. But if we want to be pedantic, ultimately there are no pure facts, as such, but only interpretations. It's all a matter of degree. Evolution is much too grand an idea to be confined within a small box labelled fact.