I tried to reproduce this issue, but could not. When dragging a single file with left
mouse button, one click is always enough:
There are two ways to drag and drop that do in fact need two (or more) clicks. First, if you drag a file with right
mouse button, Windows asks first you to confirm with one click if you want to copy, move or create shortcut, after what you get a dialog as in screenshot above, with second click to confirm if you want to replace the old one or keep both.
Also, dragging several files at once, you have to choose the action for every file, if the option Do this for the next X conflicts
is not chosen: