But that doesn't use the "find my device" netowrk. I think the parent wasn't saying, "I want an app that continually reports its location to my server so I can monitor my phone's location." Indeed, that's fairly trivial to build, but is useless if, say, your phone doesn't have internet access (like, someone turns it off or it runs out of battery).

The thing Google is announcing here is like the Apple "find my" network--it seems to allow you to use other people's devices to find your lost device simply based on a BLE ping.

That is something that is hard to build by yourself, and would benefit greatly from an industry-wide standard (more peer devices reporting locations!).