I think people are talking about two different things in this thread.
Some folks are talking about having the slot itself open-ended, so that longer, 8X cards can be inserted, but will simply run at 4X speeds.
Others are talking about having an opening in the back of the Framework case, so that cards can be installed in the 4X slot, in the Framework case.
Just thought I’d clarify there, because some folks seem to be replying to points made about one thing, when they are talking about the other.