Replication Task's "custom" Snapshot Retention Policy syncs source deletion

I’m aiming at keeping destination Snapshots for a fixed period of time (25 months) while being able to trim Snaps on the source dataset.

I thought “custom” Snapshot Retention Policy would do it but having set “Replication Schedule” to “Run Automatically”, any deletion I make on source is immediately replicated on target.

Looking at the documentation, it doesn’t seem to be the expected behaviour. The
“custom” Snapshot Retention Policy should keep them for that custom period of time on the destination regardless of the retention policy on source.

Here’s a screenshot of the config:

Am I doing anything wrong? Does " Full Filesystem Replication" impact that setting?