I would expect any mirror made by somebody else to merely meet the spec listed. If it says 1/4 wave, that would be 1/4 wave on the surface RMS which is not all that great.
Such a mirror would make a usable scope but not a great scope that would resolve to as good as the mirror size could do.
I consider that a mirror that is spec'ed to 1/15th wave on the wavefront to be an essentially perfect mirror for visual use by the amateur on earth. At that point, there will be only a few hours a year that such a scope will be the limiting factor to seeing the sky and that only at very high altitudes.