Oh, I am researching it. And noticing several interesting things about all the "info" on the topic and who is promoting it. I'm even making the effort to collate all these in a nice document, with archived links and a time line if it can be worked out. However, I do not in general doubt the existence of underground hidey-holes at all. This one is 12,000 years old and dug by hand. https://youtu.be/jKhCeFyFwzA

Nor do I doubt that such a fantastic drilling machine would be a dream for mining or disposing or nuclear waste. Or ferreting out ancient reptilian overlords, although I still maintain that at those depths there are only going to be robots. These are the world's deepest mines: https://www.mining-technology.com/features/feature-top-ten-deepest-mines-world-south-africa/ The deepest being 4 Km, but it was a big, obvious effort that would be noticed, not something that a lot of rich people could manage on the qt. Working in these mines is hellish. Imagine the ambient temperature being twice as much.

The confusion is the idea that human smugglers are going through these deep holes with kidnapped children to deep hideouts where life can only exist with airconditioning that would be even more amazing than a plasma borer. Why on earth would they do that? Every day people are found disappeared into ordinary basements. No need to go far away or use such equipment. The human powers that be aren't going to do that either. They might try to hide in places like Khazakhstan and put up a fuss if such a country was invaded, they aren't going to give up their comforts. The biggest such rich man's bunker I saw proposed some years ago had room for only a hundred people at most, and that was just a proposal someone was trying to get funded.