I see your point @demi. However, I don’t think in this particular case it will help the situation. Users won’t look for how to specifically install software X in Qubes. Rather they will look for upstream instructions (e.g. from signal’s website). So they will inevitable try to run the wget command to obtain the gpg. They’ll do all sort of things in a desperate attempt to get it to work.
In your solution this requires prior knowledge of what a GPG key is and that it’s available in the keyrings. But most new users will not know that. However, for more advanced users equiped with that knowledge it will be a nice to have.
On the other hand in @Insurgo’s solution the user will type the commands and see an error indicating a clear solution (replacing wget with wget-proxy) – something which hands the solution to the user instead of waiting for them to go look for it.