There is a simple way to tell if an apple interface is proprietary:
Is it possible for them to make it proprietary without making the system completely unusable? Then yes, it’s proprietary.
This is a company that made their bluetooth interface proprietary.
Qorvo UWB solutions enable developers to evaluate new user experiences based on location, distance and direction. Beta evaluation kits and modules work out of the box with supported Apple products and allow developers of accessories to evaluate the capabilities of UWB technology.