The author is wrong in their description. Some value types in Swift (like the standard library collection types like Array<T>) are value types with copy-on-writ

The author is wrong in their description. Some value types in Swift (like the standard library collection types like Array<T>) are value types with copy-on-write behavior. Until modified, copies of the Array are not made. That copy-on-write functionality must be purposely implemented in the type and is not something provided automatically in Swift.