I believe you are referring to dividend investing? Investing in a portfolio of stocks that pay higher than average dividends. I'm not an expert in this, but dividend stocks don't normally have as high of a growth potential so the math may be different. Usually when the FIRE community refers to investing, they usually refer to an index fund that includes either the S&P500 or global stock index so you can track the movement of the broader economy and count on the economy growing year over year.
With dividend investing, it's not really the same thing and the math likely won't work out the same.
Also, depending on your jurisdiction, you pay taxes on dividends. So, it makes sense (while you earn) to invest in shares or funds that don't give you income (they pay dividends that you have to pay tax on), but capital gains (they increase in value, but you don't have to pay tax on that until you realise the gain, ie sell).
Once you're retired, you can switch from a capital growth portfolio to an income providing portfolio.
With dividend investing, it's not really the same thing and the math likely won't work out the same.