I think you should replace "despite" with "due to" in your sentence
I think it was a comment on your speculation(s). I don't personally think high efficiency has resulted in increased noise, as I've heard many buzzing power sources and electronics before 80 Plus certification even made its first appearance. It is just, as Mike said, more obvious now.
The Corsair support person's statement is just common sense: sensitive electronics are sensitive. It's a matter of building them well enough, if we define well enough as being able to compensate for increased sensitivity while fulfilling high standards of efficiency. Nexus has done that consistently, in my limited experience, whereas Seasonics still pop up from time to time as buzzers, despite premium pricing.
As I have always had the good fortune of using grounded sockets and the same UPS, I can safely say those aspects of my "experiments" have been controlled, so it has been down to the PSUs to buzz or not to buzz.