Here we are again out of the GA context, but obviously DME/DME is not going to work where there are no DMEs, and the only ways to maintain lateral navigation will be either inertial (INS) or GPS.
Its a tool but most of the time it comes down very low on the list of Nav data.
If you have DME/DME, that is a reasonable policy. It's just that there are no GA products for that, so it's a bit irrelevant.
Preferring VOR/DME over GPS is slightly nutty but normal for attitudes from say 15 years ago
