GIT_CONFIG - what's the point?

Greetings.

Given the GIT_CONFIG environment variable can change 'git config' behaves, it stands to reason that if GIT_CONFIG is defined, then ALL git commands obey the value of GIT_CONFIG and use that file for config info.

As a test, exported GIT_CONFIG=/tmp/ohm, copied ~/.gitconfig to /tmp/ohm, moved ~/.gitconfig to ~/.gitconfig.hold and then tried git st, where 'st' is an alias for status in my config file.

No dice. git st was unrecognized.

So, what's the point of GIT_CONFIG if only git-config uses it? Or did I miss a step?

Thanks