Thank you. I was asked for additional documents twice in the process.
The first time was after I passed my medical. After submission, I went into IP1 the next day. The status after a day said 'You have uploaded' and then in a couple of days to 'being reviewed'. It was like that till in the middle of NA, I was requested for additional documents again. Interestingly, the status changed to 'We do not require any additional documents' before I submitted by additional documents and it has been the same since then.
In summary, it seems all random and status changes happen anytime.
Hope I could answer your question.