That won’t help though without also specifying the path to the correct home directory and running as a user with sufficient access rights to that. Not quite so easy on Synologys.
I think the minimum needed would be (and also independent from which volume it’s installed on):
sudo -u sc-syncthing /var/packages/syncthing/target/bin/syncthing --home /var/packages/syncthing/var/ --allow-newer-config