The v2.1 release is backwards-compatible but preconfigured_waf_config_exclusion in pre_configured_rules and custom_rulesis obsolete and will be removed in next major version release.
preconfigured_waf_config_exclusion in pre_configured_rules and custom_rules is obsolete and available for backward compatibility only. Use preconfigured_waf_config_exclusions which allows multiple exclusions. They are mutually exclusive.
If you are migrating from preconfigured_waf_config_exclusion to preconfigured_waf_config_exclusions first remove preconfigured_waf_config_exclusion and apply the code, then add exclusions using preconfigured_waf_config_exclusions