At last, an author who knows the difference between a butler and a valet. Most of these series, the people being called butlers are just personal manservants. The butler is the business manager of the estate and supervisor of the estate's staff. He only acts as a personal aide if the master of the house doesn't employ a valet.
Which is why so-called "butler cafes" should really be named "valet cafes". Although an Ojousama probably would have a female personal assistant, not a male one.