Lol, I was pretty sure right up to the point where you asked me if I'm sure

I'll check up on this when I've got some time but thinking about it logically disconnecting the N-E link on the suppliers side isn't something I'd do lightly even on a small domestic supply, I'd certainly be wary of current flowing through that link even with the DB isolated, there's fault conditions that could be occurring locally that could result in a backfed current.