Actually each application is processed on its own merit and nobody really knows the reasons for such delays.
Like I give you my example. I applied in april 2021. One of my friend who applied 2 weeks later than me, his medical appointment dates are also later than mines and we both have same type of application (postdoctoral fellowship). We both applied for spouse and kids. He received request for additional documents in July and received PPR in August.
I received request for additional documents 2 weeks ago (VO asked me for same documents as they asked to my friend). While my friend is busy in flight booking but I am waiting for decision. Considering this, VO picked my file just 2 weeks ago, however, eligibility shows that it was started on the same day I performed my medical in May 2021.
Sorting of applications by VOs is beyond my understanding. Some get their results in weeks while many wait for months