The author may be a right-wing fellow. Nonetheless, the data he exposes are taken from official Mozilla docs.
Ad hominem applies to arguments. The source of an argument does not affect the soundness of that argument.
But it’s not a fallacy to question an overarching narrative based on the source. If a person keeps selectively choosing facts and twisting words to forward a specific narrative, it’s not fallacious to view what that person says with skepticism.
Edit: Typo. Also changed “valid” to “sound”.
ad hominem: in a way that is directed against a person rather than the position they are maintaining.
If you think his narrative is skewed and based on selectively chosen facts and twisted words, you could correct that.
And other people are doing that in the comments. I addressed your point about ad-hominem specifically. So your response is kinda irrelevant to what I wrote.
People are questioning the narrative the author is painting based on their motivations. That’s different to ad-hominem.