the point is the scores are largely about box ticking and procedure, above and beyond actual hygene and certainly has little to nothing to do with quality or customer satisfaction. you'll be fooling yourself if you think a 4 or 5 is automatically better than a 3, it means they've paid lots of...
1/5 is basically they fulfill legal requirements for hygiene and nothing else. so it stands to reason those with 4 and 5s are adhereing to standards well above what is necessary to keep you from getting ill. its a bit like hotel stars, you cant get a 4th star without certain facilities...