Misunderstanding buf format and error-format?

[redeexpressos]

Hello.
When I run

buf lint --error-format=gitlab-code-quality proto/

I get an error output:

[{"description":"Filename \"Aaa.proto\" should be lower_snake_case.proto, such as \"aaa.proto\"." ....

However, when using format, I dont get any error output. It only prints the new "formatted" files I guess.

buf format --error-format=gitlab-code-quality schema/

# formatted text...

I've even tried with --exit-code but no success. I only get a error code, not the error message.

Am I misunderstanding error-format in format feature?