one more thing. Which forecast would give you a visibility of more than 9999? No TAF surely.
From the numbers and over flat territory most of those flights would have probably been possible in VFR but not much fun.
I agree that it would have been much better to use real pics. I am professionally involved with flight simulation and weather (both separately and jointly) and I am pretty clear that most sims can not display visibility accurately, far from it.
Personally, I have a feeling that this study has a different goal than accuracy and that is why I completed it. I won't elaborate but I think I can see where he is coming from and if I am right, then I guess he is onto something which will make most comments here insignificant, because it is not about what it appears.