RROC has PACE groups that do their part in NOC specific assessments, localization support, etc.
Before PR tracker, an application with all completed used to sit in a queue for long time due to NOC, language, etc - just that we never saw it in those cases(as there was no PR tracker). We've seen GCMS notes where this was the case(all completed, no PPR/RFV/portal). What we don't know is "why", could it be that the final approval takes time at RROC due to resource issues for localization/NOC, etc or simply there's a queue of approvals to ensure VOs aren't overflowing with approval requests.
If you look at the confirmation bias in this forum, practically every VO has been called slow (Montreal, Sidney, CPC-Ottawa, etc). When in reality all of those have been proven to be fast and slow at the same time.
Think about it, IRCC Delhi has a KPI of 27 PR applications/week per contractor iirc, it would make less sense to send someone an approval email and hog their passport at IRCC Delhi for months while they wait processing.
Again, all of these are just theories and are completely baseless as long as we don't hear it from an immigration lawyer or IRCC itself. Otoh, from the lawyers that I spoke to have been very shy of discussing this as they understand that IRCC at the end is going to stick to their SLAs and it should be acceptable.