diminishing return is probably true and John Bott was certainly not a beginner, that is he had a good squat before his injury to begin with. So 130kg should of course be taken with a grain of salt, besides these numbers are based on a higher bodyweight than Elliots.
Anyway I thought it might be good to give a link to a rehab squat program. I tried to get the publication of Narcessian but wasn't successful so far...
And yes I used this program, also with different poundages and only one run, during last december as you probably know and for me it did produce a significant increase in my OHS from a former best 82.2kg x 3 reps to 80kg x 13 reps within roughly a month, but I understand that you are a little reserved.