Isn't it "known to the system" which means there is an association for the extension in question ?
That is the true problem, as it is the poor user that has the problem as they don't know either those file types known to the system or otherwise. I fail to remember the number of times when we send a user to check/modify the avast4.ini file only for them to come back and say they can't find it, there is no avast4.ini file, but there is an avast4 file.
So the system know the ini file type and doesn't display it and the user is the one suffering the confusion and this isn't the only file type which could cause this confusion when trying to find a file. It seems crazy to do this as there can't be any real overhead in simply displaying all file types.
Well, isn't odd enough that something DOES have an extension even though they are hidden? That would have raised my eyebrow so why doing it the other way around and confusing users with 2 visible extensions (one real and another fake one)?
But at least when they can see all file types, they will see all the rest only have one, so would that not raise their suspicions to at least seek advice.