Thanks guys, I think I finally get it. I'd been thinking of the "ground loops" as a "spin out" and the nose-over as a ground loop. Some of the WWI a/c like the AVRO 540 and Sopwith Pup employed a skid built into the undercarrage to deal with nose-overs. And others used various sorts of skids on the underside of the lower wing to avoid the wingtip touching the ground on landings as thus presumably ground loops. I've been thinking of installing similar sorts of removable "training wheels" on a Dr1 to tame it down a bit.