cam is a top end job. nothing to do with bottom. At least he was as shocked as we are, hopefully a bad batch of cams like you mentioned.

Lifters ride on the cam lobes. and connect the pushrod to the rocker arms, rockers work the valves. there can be some significant pressure between the cam and lifters, why proper break-in is req'd. especially if you're running aftermarket springs to keep up with a high lift cam. like .5 to .6" inches of lift. I think you have stock springs on the valves and everything else is stock, so its got to be either bad cam or bad lifters or some combo thereof.

good news. a shop trying to warranty a cam is a lot better than 1 person trying to. hopefully you'll know sooner than later whats going on. I kept looking for a reason the cam ate the lifter, but weak steel is about the best explanation I can think of.