If you try to set cross-Site automatic transfer mode to AUTO using Rest API and if you have any wrong configuration like <backup strategy="SYNC"> and invoke the rest request:

 POST /rest/v2/caches/\{cacheName}/x-site/backups/\{site}/state-transfer-mode?action=set&mode=\{mode}

you will not receive any exception in the response body, the same applies to CLI if you invoke:

 site state-transfer-mode set --cache=myCache --site=NYC --mode=AUTO

The following exception should be thrown

*CacheConfigurationException: ISPN000634: Cross-Site automatic state transfer is not compatible with SYNC backup strategy*