Very nicely done.
I built something similar.
Your jig may have been an inspiration, but frankly, I built it a while back and don't recall.
Yours, actually, I think is a "fixture". A fixture is stationary and you take the workpiece to the fixture. A "jig" is mobile and you take the jig to the workpiece.
Mine is small and portable jig, but works on the same principle. So I would position it on the workpiece and then clamp it in place. Intended for loose tenons. There is an edge guide at the back that might be hard to see, also home-made. Adjusting to the center of workpiece would be done by adjusting the edge guide.
Made of hard maple. Surface on front and back to keep router flat and square to workpiece edge.
Yours is better suited for small workpieces, mine perhaps better suited for larger workpieces.