How to "Use PROFILE instead of the user’s default profile."?

[George Clemmer <myglc2@gmail.com>]

I am trying to understand and use Guix profiles. In (guix) Invoking guix
package it says ...

‘--profile=PROFILE’
‘-p PROFILE’
     Use PROFILE instead of the user’s default profile.

Because I want to use znc *instead* of the packages in my user’s default
profile, I did ...

guix package -p znc -i znc

... then I read this in znc/etc/profile ...

# Source this file to define all the relevant environment variables in Bash
# for this profile.  You may want to define the 'GUIX_PROFILE' environment
# variable to point to the "visible" name of the profile, like this:
#
#  GUIX_PROFILE=/path/to/profile ; \
#  source /path/to/profile/etc/profile

... so I did ...

GUIX_PROFILE=znc
source $GUIX_PROFILE/etc/profile

I expected 'which' now to find znc but not my user’s default profile
packages. Instead it finds znc *plus* my user’s default profile
packages.

So it looks like I am using the "union" of the znc and user’s default
profiles as opposed to using the znc PROFILE *instead* of the user’s
default profile.

Is that a correct understanding of what is happening? Is that how it is
supposed to work?

If so, how do I "Use my znc PROFILE *instead* of my user’s default
profile?"

TIA - George