Presume you may be referring to:
"
Does vSphere Replication support Storage DRS?
Neither array-based replication nor vSphere Replication support using Storage DRS. Storage vMotion of a replicated virtual machine results in a full sync, where both the primary and the recovery side disks are read and hashed, and these hashes are exchanged over the wire which can result in heavy I/O, and this can cause latency on the datastore.
Update History
8/21/2012 - added SDRS support info."
I would assume from past experience that the documentation on the site would trump what your training material - in fairness based on the above reasons it seems valid enough