Yes, it's really surprising if u r already in Canada and agree with what u said about maintaining funds in the account throughout the process. I am guessing CPC would like to make sure people didn't just put in money at the last moment right before the application and withdrew it later.
Have u been asked for the last 6 months statements with explanation of large deposits?
Yes, the evidence of settlement funds needs to be submitted in details for the last 6 months. Thankfully I didn't have any recent lump sum deposit in my history that tend to make CIC suspicious if the bank balance is fictitious. I just emailed my documents yesterday, will keep you posted if they ask for further details/explanation.