It may not be that hard to say that's its for:
- Preventing "counterfeiting" as in people salvaging their PCBs to put on "rogue" devices.
- Protecting their brand name as a "rogue" device may misrepresent what a proper sonos product actually is.
- Preventing misuse of the account that was registered on the device, hence protecting their customers personal data.
- Customers only use this mode when a product is not repairable.
That's the power of having a strong legal departement, pretty much anything can be argued even when everyone knows the real intent. When such things are done properly, it's really hard to prove the intent hence, the risk is pretty low of being fined anything.