Have you tried? Or are you just assuming?
I have seen various messages around here trying to troubleshoot the "poxy proxy" issue. Trouble is it seems to depend a lot on what is going on at the user's end, and X1 can't know that.
It doesn't help that X1 insists on using a user hostile "stub" to initiate installation. Why can't they just let people download the msi files?
Two things there where is "here"? At your end? Or in this forum?
As to the "that I know of", I'd better not respond to that.
I see what you mean now. It is buried down in the configuration of the viewers. (I've never needed it.) As the Window you are looking at does nothing when you press Help, I suspect that this is really something going on in the viewer software that X1 buys in.