Out of curiosity, I opened the Google app in iOS, searched for a place, and tapped on the result to open a map. Even with the default app set to Apple Maps, it goes straight to Google Maps.
I haven’t been able to find the correct MIME type or URL protocol for a generic geo call, either, which makes me suspect that there is more to it than it seems.
Regardless, it seems strange that other applications can show you a list of navigation apps when clicking on an address while Apple cannot. You're saying it's too technically difficult for Apple to achieve what others can?
Somehow, by some magic, Telegram asks you if you want to open the navigation to an address in Apple Maps, Google Maps or Waze (for me, possibly different for others). I'm not sure I'm buying it's too difficult for Apple to do the same, if they wanted to.
Meaning that it wouldn’t be much of an issue to open an audio file with anything that isn’t Apple Music, but FindMy would need to support a myriad of map app formats to work as intended.