And they should give the same results. In essence, both are the same.

In the first reference >> =B3*D$2 >> the 2 (row) is absolute >> so as you drag down, the row 2 reference stays the same. It's locked down as absolute.

In the second reference >> =B4*$D$2 >> the 2 (row) and the column (D) are both absolute >> so as you drag down, the row 2 stays the same and so does the column (D). So, you don't actually need to lock the column reference since you are dragging the formula down. You would only have to lock the column if you are dragging to the right and you want it to stay on column D.

Switch between relative, absolute, and mixed references - Excel