No, when you tab complete it makes it a capital d. It’s not required but it does look better imo. The single quotes prevent the dollar sign from being interpreted as a variable. In this case it isn’t required because it’s not followed by a number or letter, it’s a good idea to get in the habit of only using double quotes when you need variable expansion.
I know this has been answered, but I do this with every server I build to add a file based on the server type. I don’t use a PSSession, this a snippet of the needed code.