In the reprotect process using vSphere Replication, Site Recovery Manager reverses the direction of protection, then forces synchronization of the storage from the new protected site to the new recovery site.
When performing reprotection with vSphere Replication, Site Recovery Manager uses the original VMDK files as initial copies during synchronization. The full synchronization that appears in the recovery steps mostly performs checksums, and only a small amount of data is transferred through the network.
Forcing synchronization of data from the new protection site to the new recovery site ensures that the recovery site has a current copy of the protected virtual machines running at the protection site. Forcing this synchronization ensures that recovery is possible immediately after the reprotect process finishes.
If you want to manually set up reverse replication on a vSphere Replication protected virtual machine, use vSphere Replication in the vSphere Web Client to force stop the incoming replication group on the old recovery site, which is the new protected site. If you just delete the virtual machine on the original protected site, the reprotect will fail.