That’s probably not a bad guess, although not infallible. For sure there are cases where the AZ extends beyond 1km, and also many cases where an invalid subsidiary summit is within the required elevation range and less than a km away.
Indeed, activators are responsible for acting safely. But following SOTA rules means that the operating position must be in the AZ. It’s tough when this isn’t possible whilst staying safe, but you’ve got to be prepared to chalk it up as a failed activation. I hope everyone is familiar with the exact definition of the AZ. See the General Rules (see 3.5.6).