I think you are mis-interpreting that.
That hinge is meant to be put into wood doors (or else), where you have to cut/mill the correct “blind” hole for the hinge.
You don’t want to have the hinge visible from one side of the door (it’s an “invisible” hinge), so you have wood all around the hinge.
There is little-to-none gap, if you design correctly the holes in the door.
The hinge itself have a gap, but the gap is occupied by the door, usually.
… still, you want to have a minimum gap, because if the door touch near the virtual rotation point, huge strengths will apply (long lever), breaking your hinge …
After opening the Grasshopper file I posted above, all you need to do is switch on the Kangaroo solver and then drag the part in the front view. You need to drag somewhere close to the hinge points on the part and if the range needs to be bigger, you can increase it in the Grab component.