Note, to be more clear, an enum with no variants has no values of that type (can't be constructed), and a struct with no fields has exactly one value of that type
I wouldn't say they got it wrong exactly. Uninhabited types aren't equivalent to unit types, but in terms of Rust they're both classified as zero-size, and I suspect they were just pointing out that Rust has optimized and special-cased zero-sized types accordingly since time immemorial.