wrote:
I'm not sure about it but here's my guess: The Jepp routes are
"preferred routes" put together by ATC that take into account traffic
flows. DUAT, however, is independent of ATC and makes up some
reasonable route, where "reasonable" was decided by the people who
wrote the comptuer algorithm that comes up with routes.

IIRC the DUATS user's guide https://www.duats.com/duats_planner_doc.html at one
time claimed that it considered ATC preferred routes in its routing algorithm,
but I just looked and I don't see that claim there now.