QOpenGLFramebufferObject::release + QOpenGLWidget = broken

Going by the documentation, one would expect this:

// fbo is a correctly set up QOpenGLFramebufferObject
fbo.bind();
fbo.release();

...to be a no-op. And indeed, with QGLWidget it is. With QOpenGLWidget, however, it breaks rendering, because it does NOT set the active FBO back to the default FBO, as claimed. To unbreak things, one must use the (ugly) incantation:

context()->functions()->glBindFramebuffer(
  GL_FRAMEBUFFER, defaultFramebufferObject());

(What's more, it isn't obvious to me why this happens; looking at the source code of QOpenGLFrameBuffer::release(), it looks like it ought to be doing the right thing. Alas, no such luck...)