I really hope and think they are not working on student visas, as the September classes have already begun, I doubt there will be many applicants now. But one thing I feel is that they work in batches, last NDVO was active on 22/23 August, many people got IP2's from April/May batch.
Let's see which is the next date they chose to issue IP2s and which months are opened in them and which dates covered.
For what i have seen, people who got additional docs "not needed" on 9th August, had Ip2 on 22/23 August, hence after mere 15 days.
There are 3 routes a file takes IMO after CIO,
first is IP2 issued after 20-25 days after "not needed",
second is IP2 issued after 30-35 days from file transfer,
and last and worst is file is delayed with longer due dates and NDVO leaves it to rot for months!
So checking data for various candidates I think we will see some updates definitely by 12th September, give or take a few days, if not then I guess we might be in for longer wait, let's hope NDVO takes pity and becomes more efficient.