The QTI and QTII transfer case is essentially an electronically controlled center differential, more like an electronically controlled version of the Torsen center differentials Audi started using decades ago (that system was based on clutch packs that operated like hydraulically driven rear LSDs). Because it's electronically controlled now, they can send up to 100% of power front or rear in a fraction of a second. They advertise it as 'disconnecting' the front axle under normal conditions (presumably in AUTO/SPORT modes). This probably helps fuel efficiency.
Just my conjecture, as I haven't found any 'white papers' on the current system, but it seems like if you select SNOW, SAND/MUD, or ROCK mode, it probably activates the front axle upon selecting the mode, possibly at 50/50 (where it will otherwise activate the front axle automatically when it detects rear slip in AUTO/SPORT modes). From what I've been able to glean from various videos, cars with the rear eLSD will automatically activate the rear eLSD if it detects L/R slippage at the rear (locking it, effectively) in SAND/MUD mode, and engages the rear eLSD more quickly in ROCK mode (which requires 4 low engaged). I've also read that SNOW mode is NOT what most people might expect: It's designed to promote neutral handling, and thus will NOT lock the rear eLSD (seemingly EVER), so if you're in a low traction environment (ie stuck in the snow or driving uphill in loose/deep snow, etc) you want to be in SAND/MUD, or ROCK mode. SNOW mode is meant to promote 'stability' over anything else (ie pulling out to pass on a snowy two land road, etc).
Watching the videos of the WK2 (which also had the ZF rear eLSD) vs the WL, it's pretty clear the system was significantly FASTER to engage the rear eLSD on the WK2. This seems like a mistake, even a 'defect', but it may be by design. I much prefer the faster-engagement of the WK2, for sure.
But, with regard to the center 'diff/transfer case', it seems like if you had the keys to the computers, you could program a 'drift' mode that would lock it in RWD, and also lock the rear eLSD, and remove or dial the stability control system waaaaay down (lots of sports cars have this programming, with modes allowing more drift angle, etc by the driver).
Unfortunately, the software systems are now so secure that aftermarket tuners can't get into that system to add such a thing. Living at a ski resort in Wyoming, I would soooo love it if we could have a 'drift' mode, but as it stands, Jeep doesn't even allow traction control to be fully
disabled, which is annoying for off road use as well. When the conditions are good, I just drive my old manual transmission Xterra with its fully defeatable traction control in 2wd with the electronic rear locker engaged (have to put it in 4 low to engage it, but if you shift back to RWD, it stays engaged
) for shits and giggles. As it is, though, the WL is a 'fun sponge' in the snow. If anyone ever offers a way to enable a 'drift mode' on the WL, I will be the first to buy it.
On the WK2, someone figured out that you could pull the center console cupholders up and install a 'kill switch' on the purple wire running up the tunnel and it would fully deactivate the ABS and stability control (once ABS is off line, the stability control can't operate either). Hopefully some resourceful person at least figures out how to do that on the WL at some point, and maybe there's a way to kill the wire to the center diff that would leave the front axle disconnected as well, if RWD is the 'default' mode.
As a car guy who likes manual transmissions and complete control over things, I'd really like those options.