I have opened your workbook in Excel 2010 , and the same behaviour is present.
What ever be the font of those cells which contain the formulas , what ever be the font size , the moment a new row is added to the table , the font of those cells changes to Calibri , font size 11.
I changed one cell to text , and repeated the same exercise ; the font of all the cells containing formulas changed to Calibri 11 , while the cell which contained text , retained its cell font , font size and style.
I tried in a new workbook in version 2016 and it's the same. This could well be an old bug that has returned. On the MS community I found some older (2017) threads about this. Status closed as it was fixed (thus it is a bug).