There is no official statement on this, but you can clearly see it's the case with many applications where funds have fallen below minimum due to fluctuation changes. After all, it only makes sense.
Settlement funds are required to prove that you can support yourself and your family when you arrive in Canada. So, imagine you have the equivalent of 13 000CA$ at time of application. All is fine, you meet funds requirement at that time. But what if your currency undergoes a sudden drop due to an economic crisis, and your funds are now only worth 10000 CA$. Technically, you no longer meet the funds requirement, meaning from their perspective you are no longer able to support yourself upon arrival in Canada.
Many applicants have had their funds drop below the minimum mid-way through the process, and had their application refused because of that.
If you are right on the edge in terms of funds and are worried that your currency might be subject to fluctuations to the point of falling below the minimum, you can indeed be proactive and put some money in the account (if it's a gift, provide gift deed), and submit your new bank letter and statements via CSE.