The purpose of the bedrock and minie ball tests were from an experiment/challenge that "woodchiphustler" wanted to see done. He lives in Virginia and in certain areas of the eastern US, there are pockets of this red clay and bedrock mix. Notably in Culpeper, VA. I have it as well in my back yard...red clay and bedrock. These areas are notorious for bringing VLF machines to their knees and pulse machines working well in them It is George's theory that it's not so much as the red clay that keeps detectors from doing well there....it's the shallow bedrock under the red clay. So "woodchiphustler" started playing with different machines over the years, via balancing to a bedrock sample, setting detectors to knock out a nail, and then seeing if they could detect non ferrous items on top or above the rock. All VLF machines he's tried has not been able to pass this test...the Pulse Machines can...thus why they do so well on the DIV hunts. The Blisstool was able to as well, as seen in their video making it the first VLF to do it.
Whether the machines can find targets UNDER the bedrock is non applicable. In over 16 yrs of metal detecting I've never found anything under bedrock. Everything sinks down TO the bedrock and stops...has no way of getting under it. We've found that even with gold dredging in creeks here...that there is a dissolved layer of bedrock....the mud will turn to a greenish blue color once you hit the dissolved bedrock...and you'll find gold from the top part of the creek to the layer of greenish blue mud...and then nothing under that. Thus meaning it had came to rest on the bed rock and stopped like everything else.