On second thought, an engine builder is going to throw out virtually every used cam that comes in if not every one so a picture of a drum full of cams wouldn't be convincing.
My husband has worked as an automotive technician for every year the zinc free oil has been in use, he's seen dozens of cars come through every week, knows several mechanics, neither he nor any of the mechanics he works with have seen a systemic problem with flat tappet cams and zinc free oils. there's been no bulletins from automanufacturers warning to use zinc additives on non-roller motors, there's been no arcticles in the automotive trade publications, no one on the North American online automotive technicians network has mentioned it, the engine rebuilder that did my motor never mentioned it so I'm not buying it.
If you want to debate zinc additives further please start your own comment topic about it.