No doubt, I have come across profiles whose approvals have surprised me just like you mentioned... and quite a FEW whose refusals have shocked me, but MOST refusals that I've seen around here are hardly inexplicable IMO.
Unfortunately, there's no principle of fair and square at play when it comes to IRCC.All applications are assessed on their individual merits and the IRCC officers are trained to spot issues that might not be glaringly obvious to a layperson (which is why getting GCMS notes is advisable so we can truly see what the VO considered during the assessment). One just needs to do their best to tick all the boxes and ensure you have a strong application. If you submit a shoddy application with irrelevant course/program, not enough funds, poor english language results etc, then you are diluting your chances of success. Control what you can control is what I'm saying
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Every application is assessed on their individual merit, within the policy, training and guidelines of IRCC. Hardly is it ever the case that an application is only evaluated by a single VO - more often than not, it passes through the hands of multiple VOs and even offices. I believe this is done for quality control and an attempt at fairness and accountability. My application from South Africa was passed around in 3 different offices - local, Ottawa and was finally approved in Shanghai.
I almost gave up the idea of applying for a SP because I was so scared by the sheer amount of refusals posted here, reddit FB etc. It took me a whole year of research to put in my application as I needed to thoroughly understand what would give me the best chance at success the first time.