that the markings on the cave walls/ceilings are remarkably similar to those demonstrated to have resulted from modern boring machines in the vid?

Take a hardened chisel one day and find a rock...try to recreate. It won't happen.

I've read many of your posts over the years and am surprised that there aren't a few questions raised after viewing this stuff. It's not as if they are removing large quantities of rock by way of explosives - as evidenced by the temples in India. chipping this away is your final answer then?