The use of WP_REDIS_GRACEFUL | WordPress.org

Hey, I understand that having an error throws the expection and therefor put the site down. my question is what are the result data/value if in order to control those excpetions the WP_REDIS_GRACEFUL will be set to true?

what will be the value of any cache get ? null or the error message? and if so it can be false to be set as wp_cache_get expected return value.