If there was a prize I would award it to.......Spritenut!
After I asked the question, as a forensic engineer, I had to figure it out myself. The cut out, as Spritenut said, was for the knuckle clearance behind the grab bar on the early big Healeys. I would think that one could order the "Escutcheon" item 112 from Moss, cut a hole in the dash behind the grab bar, and make like your Spriget grew up. The piece of wood, called a Packing Block (item 111)for $25, was positioned with the cut out toward the back of the car in a big Healey for clearance for the Escutcheon (I love the sound of that word). In the Spriget, it was positioned with the cut out toward the front of the car. In my younger days, maybe, a place to hide the p*t.
Scott in CA