I’m saying a positive ROI is not the same thing as compound interest. An asset that rises in value like $SPY is not in of itself an example of compound interest.
Compounded interest is reliable, even boring. You know exactly what you'll have at any moment in time.
Your ten-year index returns are reasonably reliable, historically. But your 2007-2009 returns aren't your 2016-2018 returns, at all.
They're different concepts and deserve to be conceptualized differently, especially in the modern era, where interest rates on Treasure are lower than inflation.