Not sure I agree about the last point. You could always do a subject access request to get your score if you wanted to. Subject access request a powerful tools in this process to a few people use them.
My last point was aimed at the strengths and weaknesses provided by the person posting, rather than the theoretical possible way to access raw scores (if they have raw scores for individual categories)
You indeed could, but I worry grad recruitment get irritated and might impact the application/future application. I also don't know how it will help, as every firm does different types of SJT prioritising different things. After the PFO it might be worth doing (they probably won't remember you next cycle, and you can see why). But mostly it's so tight between applicants in these days that it's less useful than before (you might know if the SJT or application got you rejected, and by how much, but maybe almost down to luck in the small details)