Nail on the head. In the UK it's all about systems and work instructions, checklists, etc. A place can have all the paperwork in place and get 5* but in reality, the staff may well ignore it all and do their own thing, not bother checking use by dates, not bother checking food temperatures, using foodstuffs from non approved suppliers, etc.
We had a tandoori restaurant in our village that everyone raved about. Really good quality food, excellent service, affordable, etc. But they got a 1 rating as the guy owning it wasn't a "paperwork" person, so didn't keep up with the paperwork, but he had his own "systems" that he and his staff (family) complied with. Previously, he had a family member who did the paperwork, getting a 5 rating, but when they died, the paperwork got abandoned. After the bad rating, he got another family member to take over the paperwork and got his 5* rating restored. But over that period, everyone carried on eating there, getting takeaways, etc., and there was no difference at all in quality/service etc.
The health/hygiene inspectors don't actually check the food itself - they just check the paperwork. They don't stand and observe the kitchen at busy times, they don't do spot checks on use by dates, food temperatures, etc. The ratings really don't mean what people think they mean.