Well, the equipment that my company made was really quite primitive, BT-wise. They also only supported Classic (BR/EDR), and only then, for control stuff (shutter release, aperture adjust, etc.). Image data was sent over WiFi, and BT was used to help set up said WiFi.

Apple is probably the biggest offender, when it comes to custom implementations, but BT explicitly allows vendors to do custom implementations, so they aren't actually breaking any rules.