Interesting question. The two models are not comparable. I think you answered the question yourself. The Actuarial Society model we use in the Monte Carlo simulations is based on probabilities based on historical market data and some current market and economic conditions to simulate both short-term and long-term changes in yields. It models the variability and even includes "regime switching" probabilities of going from optimistic to pessimistic and back. This allows to consider the variability of returns. Given that we run that model on your entire scenario, it also allows us to consider the sequence of returns, that is the timing of your planned deposits and withdrawals in a varying market. When the yields don't change, that is not so much an issue. I'm sure some similar models are used by the FP Canada Standard Council to come up with their long-term projections as well as other factors.
For long-term projections, we encourage you to use long-term rates, and we set them to the FP Canada guideline as default, but you can change those to whatever you want.
Your default inflation rate you get is the BOC rate the day you register on the app. You're right we could put the current FP Canada projection instead. For years I had it set at 2%, the BOC target rate. But when inflation was shooting up I made that change. It would be very confusing to change it without your knowledge so we don't. You can set the inflation rate to whatever you want in RATES/YIELDS/CURRENCIES. We tell you there what the current BOC rate is, but you can set it to what you like. You can also set new rates to start at anytime in the future if you have your own ideas of where interest rates are going. Inflation should be near the top of the table of rates, but if you have a lot of rates and can't see it, just type Inflation in the search box at the top.