I think it's a specific reference to one of the tenets of Cool URIs Don't Change, which was that you should drop the file extension from URIs. So, indeed, not t

I think it's a specific reference to one of the tenets of Cool URIs Don't Change, which was that you should drop the file extension from URIs. So, indeed, not that ugly, but also, not cool, according to the good people of the W3C, back in the day.