If we assume they have three million now, in 40 years when they have 20 years of retirement left, assuming it sees a 5% annual rate of return, they will have $21 million.
Are you suggesting that they actually need ~$21 million for a 20 year retirement?
Yes, that's right. Assuming a typical lifespan, they will have 20 years left in ~40 years. Assuming a 2% inflation rate, $3 million in 40 years is equivalent to ~$600,000 today. A 60 year old holding $600,000 today does not seem like that high of a bar.
That's right. They have ~40 years left to acquire $3 million before they have 20 years left, assuming the typical human lifespan. Which, adjusted for inflation, is the same as someone who saved $600,000 over the past 40 years.
The needs of retirement should scale with inflation, so that means you also need $3 million today (in today's dollars) – which is rather high. $600,000 is not too far off what is the minimum recommended amount of saving to retire for 20 years on today, so it seems they simply adjusted that figure for inflation and then forgot that the income used to build up those savings also goes up with inflation.
Are you suggesting that they actually need ~$21 million for a 20 year retirement?