James,
The Leica accessory is listed as a 24mm on the Leica website. I would have to assume it has brightlines only for that focal distance, not others.
Leica Camera AG - Photography - LEICA D-LUX 4 Brilliant Viewfinder
Of course, one might also elect to buy several CV viewfinders for the same price (approx 300.00 USD) as the official Leica version. They won't be as luxurious, of course (plastic not metal), but any viewfinder that mounts in the hotshoe ought to work.
Jeff.