Hey @Achan it is not possible for the cUSDC/USDC exchange rate to depreciate. The Compound system is constructed such that the cToken/token exchange rates can only increase with time.
So I think that the illustration you pulled from Notional’s documentation steps through an example of the only potential scenario (cToken exchange rates increasing with time). If you have further questions on this, would you like to take them off this forum? If so, please feel free to jump in Notional’s discord and we can answer them there!
Having said all that, what could potentially happen is that Compound gets hacked and its USDC gets drained. That is a risk inherent to using Notional. So Notional users take the risk of Notional’s smart contracts as well as Compound’s smart contracts.