What do you mean? It isn't a personal prelature like Opus Dei, or is it a "cult"?
(1) Unlike Opus Dei, FSSP, and other Catholic organizations, it is not officially endorsed by or canonically incorporated by the Holy See.
(2) Its history and ideals are doctrinally questionable on a number of points - particularly its unhealthy view of the founder's mother's theological significance and its bizarre focus on nobreza.
I think he means that it's not formally recognized by the Church hierarchy.
I've heard to wacky stuff about TFP too, such as the rumor they've deified their founder.