Centreon can collect information on various systems using SNMP, that's true.
But Centreon plugins can add other methods for collecting information. In particular, App-Protocol-HTTP adds the ability to make HTTP queries and check for:
* response time
* presence of a specific string in a HTTP response
* presence of specific SOAP or JSON content
This has nothing to do with SNMP. With plugins, Centreon can and will do _more_ than just SNMP.