rsync over ssh still requires rsync service enabled on Synology nas

I am sending data from one Synology NAS to another Synology NAS using the rsync protocol (using bash script). It works, great but I noticed that if I do not have the rsync service enabled on the destination NAS the source (client) rsync will fail with rsync error: rsync service is no running (code 43) at io.c(254) [sender=3.1.2] This doesn't make sense since I'm running rsync as follows on the source(client): rsync -av -e ssh SOURCE USER@DESTINATION:/PATH Shouldn't this FORCE the rsync traffic over ssh? Why do I need the rsync service enabled on the destination (server) side? (Any Synology experts who can comment on whether Synology's own rsync binary does something special)