The article's point of view is that using unique_ptr to implement a PIMPL idiom is inadequate since it doesn't allow copying of the outer type without implement

The article's point of view is that using unique_ptr to implement a PIMPL idiom is inadequate since it doesn't allow copying of the outer type without implementing your own dedicated operators. Hence the new type which does act more like a value, leaving the decision to have the outer class move-only or copyable up to that class, without needing to write any special code.