It is a hack (or a bandaid if you prefer) from the old days. Most likely a waste of time for the parts in the picture since there wouldn't be much point in trying to correct the geometry when you have those loosy goosy stamped rocker arms floating around on the shaft. I'll attach an "old school" picture that makes a little more sense. This was an engine I worked on years ago where the customer wanted to run 906 heads and he wanted to make some RPM. We used a nodular rocker arm and then used blocks to adjust the geometry in order to narrow the wear pattern on the valve tip. It was a bunch of work and didn't really accomplish anything. Once I learned this lesson the hard way I stopped worrying about it but I had to prove to myself that it didn't matter before I could move on.