It appears that FireCalc completely ignores what you enter for the market growth percentage, and treats the entire starting amount like fixed income applying what you enter in "Fixed income returns of ...".
Here is how to see it:
Start with default settings: Spending 30000, Portfolio 750000, Years 30.
Change spending to 0.
Go to the Your Portfolio Tab.
Set the investment expense ratio to 0.
Click "A portfolio with consistent annual growth of".
Set the annual growth percentage to a non-zero number of your choice -- 1, 10, 100, 1000 -- it won't affect the outcome.
Set fixed income returns to 0%.
Set inflation to 0%.
Submit. Look at the results graph. The portfolio value does not change.
Now, change the fixed income returns to something predictable. A consistent return of 7.2% should roughly double the portfolio every 10 years. Look at the result. It doubles every 10 years.
Am I missing something?