Re: the other celebs making similar announcements. Do those celebrities live high-carbon-footprint lives and use private jets? I suspect a lot do.
Celebrities of the Met Gala mad-dress variety are already indulged in 'la la land' and given a lot of leeway (too much in my opinion) for being vacuous, pretentious and self-aggrandising. Those Hollywood mega-dollars bring a lot of hypocrisy along for the ride. Hide the drug-addled reality; promote the pointless tree plantings in the wrong places.
But Harry still sees himself as a public figure. So yes, he is judged somewhat differently, especially as he himself has framed the statement as 'officially' 'From The Office Of ... [add titles] ...' and added in Archewell, his money vehicle, and mentioned 'mental health', his money mechanism (eg Better Up, and his tying it in to Invictus).
Plus, Harry just isn't popular right now, looking at polls. The pomposity (real or perceived) won't be helping.