OK Now I understand what you are saying.

I opened a return I knew had an overpayment applied from 2020 and  looked it over, (fudged withholding to force an underpayment). 

When I get to the very bottom of the 2210 page I clicked on the QuickZoom to the underpayment penalty worksheet, and it shows the applied overpayment with a date of 4-15 and counts it in the first quarter.  Under section (a) First Installment. on the second line.

So it looked ok on mine, but the situation was different as the return was filed on time, without extension payment so I can't test what your seeing.

I do believe that you are correct that any amount carrying from the prior year as an overpayment should apply to the first quarter.