Not entirely accurate. There IS a difference, but, it's mostlty noticeable in medium/low convergence percentages.
To be more specific, a render that ended at some point between 89 and 98% convergence, will look as good, regardless of quality values, though, perhaps, in the near-maxed quality values there may be a visible difference. However, if you render the same thing twice, one on the default, and another on quality set to 5, and kill both at around a real 50% (real as in an actual 50%, with the convergence rate setting set to 100%), then the quality value makes a huge difference. As far as I can tell, quality is there to help artists kill renders as soon as the render looks good enough to publish, without needing to wait for the whole process to complete, while the default actually requires the process to complete, and, even then, if you don't move the convergence rate slider to 100%, the end result won't look so good