Are you sure? Setting the level to INFO means INFO and higher are included, so that does include ERROR as well.
That said, you’re likely looking for include to only include logs from the http.handlers.waf logger, I think.
Keep in mind that those aren’t only access logs that you’re writing there.
The log global option is for Caddy’s runtime logs, i.e. all the logs.
Access logs are enabled via the log directive which is used inside of a site block (not global options).