I don't think it's polite to call people mad. I'm sure that GTDriver has assessed the problem and judged that to go with the standard diff is the best balance between affordability and practicality. In my case, for instance, whereas I enjoy owing and driving my Alfas they are well down the list of important things to spend ones scarce resources on, definitely after family, sailing boat and new kitchen for the wife (ok, perhaps more important than the latter).
I would very interested to hear any preliminary results from your survey, Grahameo, I confess to not having checked the gearbox oil level in my GT since it was new! It's now firmly on the top of the list.