Agreed that (especially at scale) you're only as good as your local management is. But there's something to be said about company culture too, and Apple's infamous secrecy permeated all parts of the culture to apply to all data, not just Apple proprietary data. A manager that allowed employees to get away with snooping would have at the time found themselves just as fired as the snooping employees if/when word of that made it to the regional managers.

Whether it's still like that I couldn't say. From the outside, it certainly seems like some of that infamous secrecy has been toned dow. Though whether that's culture/company change or the nature of being so big that even the smallest parts of your supply chain make noise I couldn't say. At the size and rate they've grown the retail business, there's also the possibility of just hiring so many "warm bodies" that embedding that culture is more difficult too.

And being fair to this study's subjects, I'm not sure you can even say much about the managers themselves. This sort of thing would be exceptionally easy for any half way competent tech to do without tipping off their manager. Apple might have the power and clout to heavily restrict what devices you bring into the back rooms, but I suspect your average local tech shop isn't doing bag checks and device checks on their employees. Who's really going to question the local tech carrying one more thumb drive than normal? And since these are customer machines, it's not like you have corporate MDM software installed that can report when an external storage device is plugged in.