Kelpie, it is simple really. NOT.
Think of a ‘rating’ as generic, as in instrument rating, instructor rating etc. Unless of course it is specific, as in type rating.
Then think of ‘endorsement’ as specific, as in spinning (versus aerobatic) unless of course it is generic, as in tailwheel, retractable gear etc.
Part 61 was written to mess with our minds. But wait, there’s more. Stand by for Part 121 which makes Part 61 a model of clarity by comparison.