so surely you're better to do this with the tailwheel firmly on the deck?
The big difference is that instead of the tailwheel being on the deck at (say) 40kts it is not on the deck until about 15 or so, and as has been said, in a decent wind many aircraft can be brought to a stop
before the tail goes down, groundloop at these sort of speeds and you are not going to cause the aircraft much of a problem. One thing I do know is that, using this technique, I have had no problem crosswind landing a number of types that I have been told "It is a real pig in a xwind!" As far as LDR goes I agree it will not take much (if any) more, instead of doing the slowing down in the air you are doing it on the ground where you
can use the brakes, which will definitely give a shorter landing distance, though many do not have the nerve for this with the tail up (again, read Stick & rudder).