iOS MAC address randomization for personal hotspots
Since iOS 8, Apple has implemented MAC address randomization as a security measure against tracking.  It will will generate a random MAC address when


responding to a probe request (another node is scanning)
sending a probe request (the iDevice is scanning)


However, when joined, it will use it’s own real MAC address.

Basically, users can be tracked when the iPhone responds to a management packet that’s broadcast.  The device (not limited to iPhones/iPads) will respond back with a response packet that includes the MAC address of the device.  Companies will log this device when it responds and track your movements.  Apple, randomizes the MAC address so that what that entity logs is mostly useless.  It’s important to note that this isn’t limited to the hotspot function of the iOS device, but to all scanning requests.