QDataStream's online documentation does not tell about writing to a stream without associated device

Reading https://doc.qt.io/qt-5/qdatastream.html#QDataStream does not tell, what happens if one default constructs a QDataStream, does NOT associate it to a device and then writes to it.

My expectation was that the stream would go to invalid state (QDataStream::WriteFailed) but it was QDataStream::Ok, which was surprising. I think there should be some words said about using a default constructed stream.