The filter is designed that way for the simple purpose of not being able to fill it up, cat didn't want to contaminate the fuel system by putting dirty fuel in filter.( Some mechanics will pour the old fuel from old filter into new filter, this prevented that.) Hope this helps
I have 2 fuel filters on my system. One of them is mounted in the upside down position. Does this seam unusual to anyone? There is now way to fill that filter after it is changed. Or is it supposed to be that way?