Yeah, there’s a big piece of this puzzle missing.
If it was an Apple or Google tag it would make sense. They have systems for tracking those but I imagine they must have some kind of limits.
Anyway, this a $10 random tag from Amazon. Why would any phone report its location? I imagine it has to either be: officially recognized by Apple or Google; spoofing Apple or Google ids; or being picked up by some third-party app.
No article I’ve see has explained how it was tracked.