Ahh ok, well.
I called them a long time back... technically they agree to a 6 month timeline from the time you get approved in CPC-M.
Within the first month after approval they are to do an initial file review, within 2 months of approval you are suppose to be notified of an interview if required. If all goes well they agree that approval for visa should take place in 4 months, and go as long as 6 months for final decision if the case is complicated. (This little caveate is what gives them their out to prolong decisions). How easy is it to say there is a matter with your case that makes it more complicated (ie: foreign travel, differences in age, the list of possibilities is endless because they dont specify). This info is on their website more or less but it is also what they will tell you verbally. So I guess this is their very loose SLA.
Technically, I received doc request within 1 month, which means they did some sort of initial file review or they wouldn't have known that they wanted these extra docs. I am guessing at this point they technically can wait until they receive the extra docs before the start "processing"