yes, that's correct.
The air tag doesn't have any long-range wireless on it's own, It uses apple's other devices for that.
the air tag will send out a bluetooth "ping" with a randomized ID number (so any snoopers can't constantly track, the ID changes over time, but apple keeps track), any Apple device in the area will hear that ping, and forward it to apple along with the location. Any iPhone, iPad, or Mac with current software will receive and forward these pings, doesn't matter who the tag or the apple device is registered to.
So as long as your keys are within a short distance of ANY compatible Apple device, you'll get updated. If he doesn't have an iPhone, but goes to a gas station or any place with other people, chances are really good that someone there does, so the update will happen though that random stranger's phone.
If he does have an iPhone (and is on current OS) he will probably get a notification about an unrecognized tag traveling with him. This is done as a safety measure, so you can't drop a tag in a random person's bag. This only happens if the tag is away from its owner, and has been moving with you for a while.
We're still working out exact details and timing on this, Apple hasn't shared too much.
Attach AirTag to everyday items, like your keys or a backpack, to easily keep track of them in the Find My app.
www.apple.com