Apparently in the world of flat tappet camshafts the quality of the camshafts and/or the lifters has turned to absolute crap. I am not surprised and can see this happening since flat tappet camshafts are no longer used in production automotive pushrod engines. Basically it's the same thing that happened with the automotive engine oil many years ago. The chemical make-up of the oil was changed because the production car engines went to using roller camshafts and a different oil recipe was created than what was used with flat tappet camshafts. Since flat tappet camshafts are no longer used there is not the quality control for these components that was there before. The racing industry only makes up a small part of the entire automotive industry. If you haven't figured it out yet, it's all about money.
I would guess the material make-up and/or the metallurgy has changed in the flat tappet components. Finding short-cuts in order to manufacture the components cheaper would obviously be the reasoning behind it. Manufacturing flat tappet camshaft cores and lifters is a very small segment of the automotive industry since the major car companies don't use them anymore. Simple economics.
Simple economics also needs to be used to fix the problem. Racers and engine builders must unite together and protest against the flat tappet camshaft rules and refuse to use them. It will not take long before the race tracks will change the rules and allow roller camshafts to be used. Simple economics.