At one time, about a decade ago, only about 1% of float glass was suitably flat for optically coating
by the pioneers on non-optical applications, like Denglas. Now that optical coating has become available for low-e window use, productivity of suitable product has increased. But it's still inferior
to plano-corrected real enlarger glass. The specific anti-Newton pattern is critical, and will even work on both sides of the film in certain applications. But you need to test all the variables, including
film type, degree of magnification, kind of diffusion in the enlrgr head, specific enlarger lenses and working f-stops, etc. At the moment, each enlarger I have has a different kind of glass in it, or a
different set of options, because each is dedicated to a different use (different formats, color vs
b&w film, scale of magnification, etc).