It’s an implementation detail we decided to go for in order to enhance iOS background detection. On iOS, in the background, advertising packets from a specific device are delivered only once per Bluetooth scan—e.g., if iOS decides to scan for 10 seconds, it’ll only report the first packet for each device it detects. However, if we rotate the MAC addresses with each packet, we’ll get all the packets instead (because we trick iOS into thinking that these are all different devices, and we later “merge” them into a single Nearable in our SDK), and thus can do much better proximity estimation, and also access more fine-grained sensors readings.
What device and Android version have you experienced the crash on? It was supposedly fixed in Android 4.4.4 (https://android.googlesource.com/platform/external/bluetooth/bluedroid/+/aefcb18) and in 5.0, there’s a completely new Bluetooth LE API that also doesn’t have this issue. The original bug report (https://code.google.com/p/android/issues/detail?id=67272) was obsoleted.