Here's my theory.......

With an iron cam and lifters, at the microscopic level, the cam and lifter material "flow", or "give", with each other during contact.
The Schubek/tool steel style lifters are so much harder than the cam core, that only the cam is flowing during contact.
"X" amount of material flow is going to happen with a given area of contact and load. If one of the pieces is so hard that it no longer flows, then all of the displacement/flow is taken up by the remaining piece. In this case, the cam.
This additional "flexing" of the surface layer of the cam under the high loads at play work harden the cam surface, and as a result it loses it's ability to "flow"....... The surface becomes brittle........ which causes fracturing, and tiny pieces of cam break away.
This goes on continually, so it looks like it's "wearing", when in reality it's more like tiny pieces are just flaking off/breaking away.

That's my theory anyway.

I may not have it 100% correct, but I'm pretty sure that's the gist of what's going on.

If the OP had used regular edm lifters, I doubt there would have been any issue.......provided he got the cam broken in properly at the start.

I feel this is one of those situations where there was a part developed to eliminate a very specific problem in certain classes of racing engines, and it seemed like a good solution to help with a similar problem with some street applications....... And in reality...... The race car parts proved to not really be suitable for street/long term use.