I read the article you linked, and it seems to me to be more of an argument in favor of a position, than a neutral treatment of the matter. At least that was my take on it.
Also, it was written 112 years ago, and I can't help but think that more scholarship has been done since then.
The author's bias seems to shine through especially in his treatment of the anti-Chalcedonian letters attributed to St. Simeon which were contained in Syriac manuscripts in the British Museum:
But the question as to Simeon's theological position during the last years of his life---that is, at the time when the above-mentioned letters to Leo, Basil, and Eudocia, are supposed to have been written---is raised anew by the three hitherto unpublished letters of which, mention has already been made. All three are decidedly controversial, and in them the Stylite speaks as a bitter opponent of the Chalcedonense.
He admits that they had not been the subject of much study, but he still comes to the conclusion that they are forgeries. Like I said, this was 112 years ago, and I am sure others since then have studied the manuscripts more in depth.
Again, what I have heard is that none of the letters are universally accepted as reliable. I think people will just believe what they want about the saint.