Dear Christopher,
besides any historical consideration, you'll see
two very good and very different modern players using right arm motion while
playing divisions: Paul O' Dette, and Hoppy.
The reason why I do it and would recommend it is
that, even willing to use just the fingers to pluck, you would have to move
your arm to lead them to the right place (course). There's no way you can
play some very difficult pieces (fast runs from the 1st to 6th course)
without moving your arm... at least if you play thumb under.
Also, after a bit of work, using the arm allows us
to obtain a much more lighter and "vocal" diminutions, and a wide dynamic
range, which is harder to obtain only using the fingers (the sound tends to
be tight in my experience, even when you have the tip joints relaxed-which
is great).
Best,
Ariel.
