I've always seen them roll the edge over with an edger.
My dad is 87,he is a retired mason,the man said it's been done since he started doing in in the late 30's
The picture from the OP is a heck of alot more than "rolling the edger over" which typically means tipping the last few inches of the slab aggressively away from the door. That lip is uncommon here, likely less than .5% of garage have them here, especially new ones.
IMPO, 1.5" ledge is dangerous, and possibly an over-compensation by a poor concrete crew that can't make the slab shed water sucessfully with less pitch........