Entered 2020 Form 1099-R in TT for Tax Year 2020 (TT 2020) and Got Warning

(1.) TT asked me what year was stated on my 1099-R: 2021 or 2020

(2.) I selected 2020 because that's what it says "2020 Form 1099-R"

(3.) TT then said because it said "2020" I am not supposed to entered this 1099-R data into  TT2020 

(4.) Instead TT said I have to amend my Tax Year 2019 return and enter this 1099R data in that return.

(5.) Why? I dont' understand.  

(6.) Also, for now I kept the 1099-R data in my TT for tax year 2020 and TT doesn't flag it as an error. 

(7.) No idea what's going on.  

(8.) Should i just keep this 2020 1099-R data in my TT return for tax year 2020 OR amend my tax year 2019 return with this 1099-R data? So confused. 

9. Thank you to anyone in advance who can help me understand this.