What? What you wrote doesn’t make any sense. Why would you have to disable the device in order for it to work? And what does “in secret” mean? What are you talking about?
The sdk documentation is on the developer website. Your description bears no resemblance to how Apple says it works.
Seems you really don’t understand.
I stated it (FindMy) will work IF disabled - as in when someone steals your iPhone and powers it off and turns on AirPlane mode .
Source: https://www.apple.com/ca/icloud/find-my/Apple:
The Find My app makes it easy to locate your Apple devices and keep up with friends and family. It works on iPhone, iPad and Mac — even if your missing devices are offline. And your privacy is protected every step of the way.
Makes sense now?
PS: UltraWideBand was the technology only on newer iPhones I was trying to mention as well when I said the name of the technology escapes me for the moment.