If I'm not mistaken, you have to be actually traveling (i.e. beyond the house) with an unknown airtag for it to start alerting you. If your neighbors are not traveling with you places, it's probably not what's going on.
I’ve been notified of an “unknown AirTag” while I was home. When I checked the locations it was seen with me, it was a random zigzag within a block or two of my home.
I’m pretty sure what happened is that the AirTag belonged to one of my neighbours, there were some GPS distortions happening that made my phone think it was moving slightly, it kept hearing the AirTag’s signal, and it assumed I was being stalked while wandering near home. This person might have the same thing happening to them.
As soon as the new neighbor moved in I got airtag notifications for days until I silenced them. I can see the prompts being scary/confusing for a lot of people. It basically says "unknown airpod is following you around!!!!" almost making you think you have a stalker that put one on your car, when really its the neighbor getting home from work and tossing their keys on the counter near your wall.
Seems pretty easy to do on popular urban trails to be honest. Some of the trails in my town have a group of people every like 30 feet and its pretty easy to end up keeping pace with them the entire hike unless you walk faster and pass them up.
They're 70 years old. I'm sure seeing "AirTag found moving with you" is confusing them and possibly freaking them out.
I bought the airtag for my dog, but now am having second thoughts, I'm just imagining all the freakouts I'll cause when walking on trails.