Proxy documentation is not clear

[ng0]

doc/guix.html/Build-Environment-Setup.html#index-http_005fproxy reads:

The daemon also honors the http_proxy environment variable for HTTP downloads 
it performs, be it for fixed-output derivations (see Derivations) or for 
substitutes (see Substitutes).

If you are installing Guix as an unprivileged user, it is still possible to run 
guix-daemon provided you pass --disable-chroot. However, build processes will 
not be isolated from one another, and not from the rest of the system. Thus, 
build processes may interfere with each other, and may access programs, 
libraries, and other files available on the system—making it much harder to 
view them as pure functions. 


... This links to:
doc/guix.html/Derivations.html#Derivations
and
doc/guix.html/Substitutes.html#Substitutes

where the substitutes page reads:

Substitutes are downloaded over HTTP or HTTPS. The http_proxy environment 
variable can be set in the environment of guix-daemon and is honored for 
downloads of substitutes. Note that the value of http_proxy in the environment 
where guix build, guix package, and other client commands are run has 
absolutely no effect. 


None of these pages provides any example or further explanation on how
this could be achieved, for example to make Guix use a socks5 proxy
systemwide. I know how this can be achieved with iptables etc, but it
would be better if the documentation is fixed. I have no idea how in
this case as the documentation is not clear.