All 16 look bad, engine is tight to turn over, lots of glitter in the oil, etc. all point to a general error, not a specific cam related problem. My guess is that the engine has a basic machine work error or an assembly error. Piston clearance too tight, bearings too tight, or something along that lines. Engine filled up with cast iron dust and everything went down hill fast. It is also possible that it was just a soft cam, but if it was me I'd double check all clearances in the rotating assembly to be sure.

I've never seen all 16 lifters fail on break in. It is usually only one lifter that fails although I have seen two a few times. But never 16. I doubt he had 16 defective lifters but it could have been a soft camshaft. I've never seen a whole cam that was soft but it could happen.

I did see an engine where the owner installed extended tip spark plugs that were so long the straps interfered with the valves. That engine turned into junk very quickly. Multiple bent valves, bent pushrods, lifters wiped out, cam lobes wiped out, etc. Just because the guy installed the wrong plugs!