These types of surveys are at best directionally accurate, as I doubt their 8000 teens are a representative sample. Are we to believe that 20% of teens own an Apple Watch, as this survey suggests?
They admit to focusing on middle class to high income households, so they might not be far off in those groups. Definitely not representative of the whole country though.
I totally buy that Apple has a very strong brand with teens, I just don't see smartwatches as being must-haves for teens. I'd guess more teens would want to put the extra $$ into a newer smartphone (faster & with a better camera) instead of a secondary device.