I have this sheet metal part that has a down 90° tab.  There is some discussion whether or not a relief is needed (see picture below). I haven't worked in sheet metal in a number of years but I seem to recall that this relief was needed by our shop to create the bend.  My problem is I can't recall why.  I am hoping some of you sheet metal experts can confirm if this is needed to make the part and if so why?

Thanks,

Steve