What this and Khan’s previous studies shows is that it really comes down to the technician who touches your device, not the chain you take it to. These employees aren’t bonded and have no loyalty to customers or employers; some will follow the law when they think they’re not being observed, and others won’t.
Takeaway: take your devices to someone you trust AND assume they’re looking through everything they have access to. Same as mechanics, washing machine repairmen, etc.