There's some amount of luck and marginal effects that need to be discounted, otherwise you couldn't say "nothing positive" about a diagnostic that always says "you are dying", and you couldn't say "nothing positive" about a strategy that has you pick the opposite route and then repeat as many times as you want. And I think such a conclusion would be very dumb.

I'm not making a statement on whether the apple watch in particular is close enough to that line.