When you do freeze panes, two border lines (not so thick) with grey color are inserted horizontally and verstically based on freezepanes method arguments, so it is natural that width and height of the grid area is increased a bit.
The 1st and 2nd parameters determine the position to be frozen. The rows and colomns before these tow parameters are frozen. That means the rows and columns are fixed and could not be scrolled.
The 3rd and 4th parameters determine how many rows and columns should be frozen. By default, they are the same with the 1st and 2nd parameters.
So setting the row and column to the maxrow and maxcolumn doesn't make sense. And it will cause the grid's height increases.