Create a table with more than two columns and two rows (though I’m not sure if these conditions are either necessary or sufficient; I wanted 11 rows and 8 columns). Change the font size of the leftmost cell in the first row to 9 points. Type a column title in that cell. Change the font size of the second cell in the first row to 9 points. Type a column title in that cell as well.
Drag select all the cells in the table and change the font size to 10 points. Deselect all cells.
Now check the font size of any cell except the two that contain text. I betcha their font size is not 10 points.