As for the big companies you mentioned, I think they always try to protect all possible processes, whether it's production or repairs.
Not an excuse for Apple, as they themselves published the process
that would be done at a Genius Bar on their own website, they just conveniently omitted that the customer would not be allowed to see it happen & witness no data exfiltration, only firmware password removal.
Imagine thinking it's acceptable to order a drink at a bar, and god knows what happens to your drink mixed behind closed doors.