Of course savings accounts have exponential growth. They're one of the canonical examples of exponential growth that high school math students first see. Every year you're gaining more and more. Flat growth is when you're growing a fixed amount every year, which means that your percentage growth would be falling off each year.

Freeloaders, *particularly* the annoying ones who whine for help or complain about limitations, are useful themselves if only for providing a broader sample of how the project works in the wild.