This is just plain ignorance by someone who clearly is not hearing impaired himself.
I, on the other hand, have profound hearing loss, almost to the level of being actually deaf. I wear hearing aids because I rely on them as much as you rely on your legs and arms. Without my hearing aids, I cannot understand what people say, unless they use sign language.
Gimmick or not, I will certainly use this feature for detecting my door bell. It’s one of the things I can’t hear without my hearing. I think it’s really worth testing. As with everything Apple develops, it’ll become more reliable in the future.