@scalman I have a SJ and have encountered all different scenarios you thinking here:
a. Stall: yes SJ model or newer 14-18 will stall but i think it is more of a function of computer aka ECU or TCU that cut power generate from engine/tranny to wheels. I think Subaru Engineer is trying to do this to protect their weak CVT from excessive force/torque. When does it happens?
1. Steep incline and your wheels lost tractions - spin
2. steep incline and encounter an obstacles like rock or deep rutted hole. Either of this required more power or causing lost of traction like in #1.
3. Steep long incline (when it is really steep) and you don't have enough momentum or have to stop mid-climb.
4. Steep long incline in sliding gravel: similar to #1 causing of losing traction after mid climb.
b. 2-pedal method: This works great not only subie but also for most modern AWD system with Torque vectoring (brake based type). Even with Xmode and due to open-diff, i experienced few times where car just spinned wheel aka lost traction and trigger #1 thus causing the stall. Lately (before my locker), i've been using this 2-pedals method with great results. It really helps to trigger the brake early on and help transfer torque to wheel with traction via the torque vectoring and allow me to get out..
3. xmode v1 (prior to 2019 Dual Xmode): it works good most of the time.. However, it is not a solution to all.
I hope to find more information what xmode does to center diff aka even distribute of power front/rear?
4. Rear locker: in all scenarios earlier, I had to use a lot of momentum which famous in subie world to tackle an obstacles. However, it easily damages vehicles and unsafe when the trail is narrow with cliff. Since i have my rear locker, i found my SJ is more well-connected to ground aka tractions, and not having to use a lot of momentum as before. I have a turbo version thus able to keep it in 1st or 2nd and slowly go up steepy gravel hill (car will slide down on its own even in park), or rocky surface. I knew the differences because i would have to floor it before in similar scenario and let momentum to carry me home.
Another note, with this rear lock my XT SJ seems to prefer distribute power to rear quicker and more often than before as it recognizes more traction there. I wish I have more proof but it seems to transfer more power to rear when climb via my ActiveTorq monitoring app.