Nothing is by mistake. At this level, the chance of mistake is very rare. The refusals are not justified what-so-ever. They either outright refuse an applicant or at least provide refusals for something that makes sense. I am 80% sure that Abu Dhabi VO didn't even properly looked at those applications. The only option left here for these applicants is to order GCMS notes and check the refusal reasons. If enough students have somewhat similar refusals with SAME initials than it can be raised as complaint to IRCC for that specific agent for discrimination.