Why is the Two Knights Controvrsial?

I recently bought the book "The Two Knights Defence" by Jan Pinski (First off, let me tell you not to buy it if you are below 2200), and in the description, it says that The Two Knights is a controversial opening. I personally really enjoy the Two Knight because after 4. Ng5 I can play the Traxler counter-attack with 4... Bc5 (I have a 20+ win streak with the Traxler currently), and The Two Knights follows all opening principles, so why would it be controversial?

What line is the "Two Knights Defence"?

It's answering Nf6 to the Italian. And it's completely sound, there is nothing wrong with it.

The Traxler counter-attack however is rather unsound.

Ok I googled it. For other uninitiated people like me:

1. e4 e5 2. Nf3 Nc6 3. Bc4 Nf6

They probably say that it's a controversial opening because "controversial" sells books.

I think when they're talking about the Two Knights being controversial, they're referring to 4.Ng5.

Unless there's a newer update I'm not aware of, that book is from 2004. There are several openings that might have been called controversial two decades ago, that are normal today.

Also, I think the word controversial only appears on the back cover, and it's common for authors to have little or no control over what text goes there. It might have been written by a publishing house staffer thinking it would sell a few extra copies.

The Wilkes' Barre' is Controversial is a Statement of Fact @Orciety

Is there much controversy about 1 e4 e5 2 Nf3 Nc6 3 Bc4 Nf6 4 Ng5 Bc5 5 Bxf7+ ?
"... 5 Bxe7+ is ... the reason the Traxler is hardly ever seen in games between grandmasters. ..." - GM John Emms (2018)

the main line after 4. Ng5 is 1. e4 e5 2. Nf3 Nc6 3. Bc4 Nf6 4. Ng5 d5 5. exd5 Na5
and now white can force win a pawn, if not two, but i dont think its known if winning this pawn is actually an advantage.