Dual drive is sort of normal, a normal Sachs/SRAM 3 speed plus a Normal cassette
and a cassette driver, made to do that .
combines the 2
Though as a wide hub dropout at 135 you could retrofit a Rohloff hub in it, and drop the derailleur entirely ,
unless you need it for chain tensioner , their Chain thing is like Rear derailleur , just doesn't move sideways.