You misunderstood my point. LocalSend is great. It does exactly what it promises, and works well.
But you're claiming "AirDrop = LocalSend" and that is not true and causes false expectations. People used to Apple think they can use it in all the same situations and for the same things, which they can't. Just because you mostly used it in the same network doesn't mean most people use AirDrop that way, and I know quite a few that mostly use it while out and about, meeting new people etc.
The "Good advice" version is too tell them there is LocalSend, which can do quite a few things like AirDrop, but not all. Basically make it clear they need to be on the same network.