That criticism sounds valid to me. That's a lot of children, and it's not like 10 is some sort of cut off point for anything.
According to what I find from a quick google, average height for a 10-year-old is about 4.5", with it starting to spike up dramatically at the age of 12-13 (from ~50 to ~60"). Without knowing the actual height they set this for, though, it's impossible to say how many kids they would or would not get with this kind of advertising.