I would say that the root cause of this issue would be an outlier.

It reminds me of when my high school shop teacher gave me a good lesson by asking me to diagnose a car that was missing on one cylinder. He mentioned that it had new plugs. I checked the entire ignition system before going back a finding one of the new plugs had been dropped prior to installation and the gap was closed. The lesson is that if your hypotheses, or premise, assumes any false information you will be fighting the wrong battle to solve the problem at hand. In this case it was originally assumed that the engine was assembled correctly, yet eating parts at random? No, incorrect premise. Clearly something was not correct. Did they mention the original p-to-v clearance on the intakes?

Knowing that it was a mild cam and it wasn't spinning high rpm would these symptoms be indicative of a mechanical interference occurring? I guess the lesson is to keep that bore scope handy lol.