That’s basically what happened to mine- it looked good for about 3 years, and then it got pretty dull. It didn’t really flake off exactly, or if it did, it was micro-flakes. But it definitely lost its sheen especially on horizontal surfaces.
I suspect they do minimal to no surface prep other than maybe washing it first, so I suppose that doesn’t do wonders for paint adhesion.
Guy was going door to door, looking for work. At one house, the homeowner told the guy he could paint his porch, and that there was a bucket of paint and brushes back there. About three hours later the guy comes back to get paid. As the homeonwner is paying, the guy says, “oh by the way, you don’t have a porch, you have a Ferrari”.