I read a similar thing recently about how "most pet owners" don't know the correct diet for their animals, and a whole host of other things. Nice and vague.
I might not know for sure how old Bert (our newly adopted stray) is, or our eldest cat Hannah, but I know their favourite foods, I know exactly where they like their chins tickled, they are all neutered, vaccinated, up to date with flea and worm treatment and get very regular health checks. Not to mention the love they get... Not knowing the age of a cat is not the be all and end all.
My vets seem quite surprised when we go in and we know our stuff or have noticed things in our animals that need investigating. I took one of my rabbits in for a tooth check as she had been grinding her teeth, and the vet said "how on earth did you notice that?" I just looked at her and said "I spend time with my pets." Sad that she was surprised, actually.