Do all these calculations account for the volatility of the market? Like, in 2017 the price reached $20,000 and year later it dipped to $3,600. The goal of stacking sats is to lower the risk of buying at the top and experiencing a crash, and this strategy performs best when the market is bearish or very uncertain. If you just make some linear upward extrapolation into the future, it might be way off the actual results.
I think it only calculates the current price that you put in the calculator. For example, you say $8,000 in the future, it will calculate your holdings in that price. Why don't you try it? It's pretty easy to understand and it's pretty useful too when you want to be motivated to save dust money. Also, it's not like Bitcoin will stay $8,000 forever according to my prediction, we could potentially reach more than $10,000.