so… as an update…
I stopped/disabled the fog replication service and used the same command as fog used to replicate the folder over from the fog images store to the synology images store.
After this, imaging from the storage node works as desired.
I’d really like to know how fog winds up pulling the Synology home page during the file compare… is it using http? what path is it trying to hit? I can set up a packet trace and try to find out, but I’m hoping someone can just chime in with the info.