I think this is because he was responding to Phil Lawler. Vigano's writings continue to change depending upon his audience. I would like to see what he writes a sedevacantist.
I very much doubt that sedeism is on Vigano's radar. He has too much sense for that.
"This forum is a space for discussion to defend the Catholic Faith following Monsignor Marcel Lefebvre. It is therefore not for rallying to the conciliar church nor for sedevacantism"
- From the French Resistance forum (Francophone forum, in France)