Retirement tax questions

Hi, I am actually trying to get clarification on my question, hopefully not adding confusion for others. I did just find something on IRS website that clearly states you can use 2019 earned income to determine the tax credit.  It would be helpful if it stated, "even if earned income was zero in 2021".   I was concerned about the fact that earned income is required, but this below does clearly state that one is replacing current year with prior year for this purpose.  

I do not about applying this to both years, but it seems reasonable and would make sense as to the purpose of the Act.   

Election to use prior-year earned income
You can elect to use your 2019 earned income to figure your 2021 earned income credit (EIC) if your 2019 earned income is more than your 2021 earned income. Earned Income and Earned Income Tax Credit (EITC) Tables | Internal Revenue Service (irs.gov)