Earlier quoted context omitted.
What's FIRE?
Financial Independence/Retire Early The core idea is to define your annual expenditures (let’s say $50k), a long term investment strategy you personally feel comfortable with (say 5% ROI), and from there you can deduce the amount you need to save to be financially independent (in this case, $1M).
Could you elaborate? Why would you need a level of comfort with an ROI? Or is the thing you need to be comfortable with actual the risk involved in getting that target ROI? Is that what you mean?
Also is the "million" you mention just a hypothetical? Although a million is a lot of money I don't thinks it's enough it's large enough to to qualify as being financially independent no? At least not in the US or EU. You would still need to work full time as it's not enough to retire on.