It would be nice if Ponz were to defend his claim with concrete analysis instead of saying that he's holding back. If this opening meant very much to me, I'd wade in and try to work out what Ponz is hiding. But it just doesn't. And that's the entire reason that both Magnus Carlsen and Hou Yifan played it: nobody studies it in depth.
There are published challenges to Ponz's book, citing errors and lacunae in the text. He's aware of some of these criticisms. Marin offers a comfortable line for Black to play. Gustafsson, in a Chessbase DVD, gives a line that is good enough for equality. Kaufman offers a line that gives Black practical winning chances.
One game mentioned in the reviews which challenges Ponz's book is W.Ottenweller-G.Aalderink, email 2005.
Ponz, do you plan to write a second edition that will deal with these and other criticisms of your book?
Fear, the problem is this particilar line is one of two "refutations" to the Ponziani and the theory is very complex and will not be settled here on this forum at this time.
99% of the lines, sure I can and have given lines and counter lines. But this particular variation is so complex that a book could be written just on this line. It may come up in a vote chess game or some other venue and if it is vote chess will use what I have. But until I can complete the theory pertaining to this line--No use going into this particular line futher, If someone wants to express their views fine .