my back is wrecked it gets sore really easy and even in plank position lower back gets fatigued really easy. years ago i strained it while squatting for a couple weeks i could barely walk when trying to spar or do any workouts now even today its really tender im not sure if i need to just get it stronger if its weak or if i messed something up =[ i been wanting to get back stronger and get better posture but scared to squat from what happened years ago
IMHO, don't get obsessed with a support exercise. If it causes pain/discomfort, don't do it. There's other exercises that can take it's place, strengthen you up, and maybe you can revisit it with a better base.
People become obsessed with exercises, even when it causes issues. Back when I was getting into jumping, I was dead-set on being able to go deep. My hip & knee ended up hurting, kept pushing through it, made it worse. Felt like an old man. Said fuck it, switched to half squatting, felt great, made my gains, never looked back. So I dropped the idea of deep squatting. Then years later with running, wanted to incorporate squatting again. I did, started getting achy, knee/hip started hurting, felt like an old man. Dropped squatting completely, felt great, never looked back (and that's why I don't lift with running - feel healthier without it).
Long story short: don't put a support exercise on a "pedestal"
As for LBSS, he has much more experience squatting, so it's easier for him to get back into it. However, with his shoulder injury, might also make sense for him to ditch squatting for now, do other stuff which creates similar tension but more safe (lunges, db overhead press, barbell overhead press, stepups etc), stuff like that, until his body is more prepared to handle that kind of positioning. Then at that point, slowly bring back squatting etc.
Squats are great, but not when they cause problems. X exercise can be great, but not if it causes pain/discomfort/problems.
Ditch it quick, do similar but safer assistance instead, perhaps re-visit it later.
pc!