I think anybody that has ever built a motor has wasted a flat tappet cam, it happens but in your buddies defense it seems to be happening more now than ever.
Alot say it has everything to do with the removal of the zinc and other antiwear agents they cut back in oils over the years due to EPA restrictions, maybe thats the culprit, some say the cam blanks aren't what they used to be, cores softer, cheaply made lifters etc, I dunno, it might be a combination of the two.
I do know, when I build a flat tappet cam motor or any motor for that matter, I pay attention to the lifter bores, they need to be smooth as a baby's ass IMO, sometimes when you get the block back from machining it will start to rust up with a quickness, the lifter bore is no exception.
I immediately clean and lube them, then check to make sure the lifter spins freely in each bore and with zero bind.
I will check every bore and every lifter to make certain of this, if any are sticky, I'll use very fine wet sand paper (600-1000grit) in the bores, then clean and re-lube generously with motor oil.
My 2 cents>Cp