I've just noticed that a call to replaceOne() also includes in the updateWriteOpResult the replacement document, in the undocumented ops array.

Is this intended? For large replacement documents, this could be a performance problem.
Also, this behavior becomes identical to findOneAndReplace() called with returnOriginal: false. My expectation was that replaceOne() did not return the replaced or replacement document.

In any case, it would help to document the ops array.