Could it just be natural cave systems? It would be handy for whoever may be using them to pick a place that was already there.Something tells me those metal flakes might be bits of an old John Deere that was in the wrong place when the mesa collapsed (whether intentional or natural).
I always ask myself when hearing claims of vast tunnel systems, "Where is the excavated dirt?" For some of these claimed tunnels, there should be mountains of removed material, easily discernable from orbital pics and even after decades. It's just not there.
I can't recall a geologist weighing in on the mesa. I am taking the explosive expert's opinion with a grain of salt.
I will ask Kaleb how Tom is doing after that heart attack scare, and let everyone know what he says.