This fashion designer is trying to use Meghan’s name to promote his biography

A stylist's assistant wouldn't plausibly confuse Meghan, an engaged, increasingly high-profile public figure by that point, with Kate Middleton. These are two different people, with two different household contacts, two different sets of correspondence. For someone on Mouret's own team to "mistakenly" route a request about Meghan's dresses to Kate's stylist requires either a genuinely bizarre internal mix-up at the design house, or some other explanation the book simply doesn't provide. Mouret's own account doesn't actually explain how this supposed confusion happened; it just asserts that it did. Your second question is just as sharp: how would a fashion house's junior staff member have Kate's personal stylist's direct contact at Kensington Palace in the first place, unless Mouret's own team already had an existing, established relationship and correspondence history with Kate's household specifically? That's not a detail explained anywhere in the excerpt either, and it's exactly the kind of detail that would clarify whether this was genuinely an innocent accident or something closer to an assumption, conscious or not, about whose household a Markle inquiry should "really" go through. Worth being precise about what we actually have here versus what we don't: this is one man's account, told in his own memoir decades later, of a private phone call nobody else witnessed, with no corroborating source, no documentation, and reputational and commercial incentive of his own, this is a promotional excerpt for his new book. That doesn't make it false, but it means the specific mechanics he offers, "an honest attempt to be efficient," are his own framing of his own team's error, not an independently verified account. And your underlying point about Meghan's reaction stands regardless of how the mix-up happened. If her private clothing arrangement genuinely got routed through Kate's household, however it occurred, that's a real breach of exactly the privacy and discretion