For people who do not work in on-board systems:
This is an average deal, as he managed to get debug permissions on the AirTags. When you have an IC like nRF52832 in a production device, the debug interface is disabled through software. By disrupting the power supply, he was able to cause the CPU to skip the “disable debugging” instruction and opened the doors to black magic.
Debugging interfaces work very differently in on-board devices. They are directly connected to the CPU and can control it directly, including reading the code (once protected). This means that future development of exploits will be much easier, as there is now a debuggable copy of Apple’s firmware that can be used to play with, while still having full control of the device.
Therefore, at the moment it is indeed not very useful. However, this is a step to be able to develop complex feats much more easily.