Thanks for the correction!

The "problem" is that android doesn't just encrypt data; it uses full disk encryption. That means, only things absolutely necessary are accessable before the password is entered. This absolutly necessary stuff does (to my knowledge) not include any diagnostics tools a technician would need to verify the existence of a problem or wether it has been solved. The new mode would probably just be a way to get more of the system decrypted so the technician can do their job.