During re-protect, vSphere replication does not delete the disks from original protected site and instead it will use them as seeds.
Status would reflect as full sync, however it does not transfer any data at this stage. It performs checksum operations against existing disks to determine which blocks are out of sync and then only replicate recent changes. vSphere Replication must read the entire contents of both the source and target virtual disk files. This operation can be very time consuming and is a expected behavior when using vSphere replication.
Refer this question 'What are the replication and synchronization types in VMware vSphere Replication?' at --> vSphere Replication Frequently Asked Questions (FAQ) - The current version of this doc has moved to: https://storagehub.vmware.com/#!/vsphere-replication/vsphere-replication-faq
I hope that helps
Thanks for the information, that clarifies my doubt.
What was confusing to me is that once VMs are reprotected and everything is reversed, vSphere Replication says is doing an Initial Sync and the definition of an initial sync in the documentation is this: Initial full sync: vSphere Replication creates an empty virtual disk at the target location and replicates all data containing blocks in the source virtual disk to the virtual disk at the target location
Now based on your comments and in the information from the link you shared I understand that even thought it says Initial Sync its mostly performing checksums