OP's example is reminding him to turn oven on or off.
Nope, it's turning it on
The paragraph after what you quoted:
[instead of buying a new oven]..
"Or I can walk over to the oven, turn it to 450, and say “Hey Siri, set timer for ten minutes” and wander off. When my wrist buzzes, I go stick a pizza in the oven and I say, “Hey Siri, set timer for thirteen minutes” and go do stuff.
I don’t need a new oven. I don’t need to worry that I’ll pick the wrong oven."