Yes you are right. I believe, as a best practice any environment where surrogate keys are generated to track dimension or for that matter for any form of versioning are not meant for truncations, especially DWs. RI enabled ODSs with no versioning proceses based on surrogate key may be good candidate. But Ideally, as noted in the summary it is useful upstream and downstream of the DW, it becomes especialy useful in EDW project where you are trucating data in an RI enabled staging area(s) for mutiple source systems, for instance where you are integrating data for corporation with many different companies.