@malfeasance summed up things nicely below.
I should also note that the above routine I shared is a template more than anything. For instance, this latest lower day I actually did do belt squats on the pit shark as my main movement. I agree the belt squat can be somewhat uncomfortable but I found this is more so to do with the actual belt attachment - the one at my gym was abused and worn, once I purchased my own the pain went away.
I can’t do anything spinal loading without pain so I’ve had to adapt my training. Heavy traditional squats and the like are a no go. My legs actually respond very well to leg extensions thankfully.