By that reasoning dom0 is not offline since it is trivial to set up a two
way interaction from dom0.
There’s a good argument for locking down what the proxy can be used for.
tinyproxy used to be restricted, but was opened up for convenience.
I restrict use of apt-cacher-ng to named sites.
We’ve discussed this before.
I never presume to speak for the Qubes team.
When I comment in the Forum or in the mailing lists I speak for myself.