I believe you may have missed what these folks are doing differently.

To put it into context, geothermal energy that taps underground water reservoirs near heat sources has been shown to cause earthquakes and other not good side effects. All of those effects are associated with water being released from aquifers that were previously sealed, or ground changes due to water incursion into previously dry structures (which happened in the reference German town).
These guys however are digging below all of that. In fact finding water that near the surface would likely cause them to determine the location unsuitable.

Modern geothermal plants are "binary" in that they have their own water loop which goes down, gets heated, and then comes back as steam. A good explainer is here: https://www.eia.gov/energyexplained/geothermal/geothermal-po...

What these guys propose doing is essentially drilling into rock 6+ miles down. That is about 5 to 10 times deeper than current plants. Using the heat from the rock which is near 1000 degrees to heat water that they pump through it into steam and recover through the turbines. The whole "pipe" from well head to return is nominally sealed with the vitrified walls created by the microwaving process.

Let's assume (and I don't know since I don't work for these guys but we need numbers if we're going to guess at things) that their "drilling" with microwaves technology leaves behind a 12" diameter hole that is > 6 miles deep. And we can drill two of those holes in such a way that they meet at their maximum depth. I'm imagining holes that start on the surface 100+ yards (or meters) apart drilled with a slight angle to meet when they are 6+ miles deep. How much power could we expect to get out of that?

So let's do a little math, water weighs about .03621 lbs/cubic inch. And a 1ft tall, 1ft diameter cylinder of water would way about 49 lbs. A mile is 5280 feet so a mile high column of water, 12" in diameter, would weigh 258,851 lbs, and a 6 mile high column would weigh 1,553,283 lbs (a bit under 777 tons) so the force at the bottom of the column would be about 13,734 psi. At 935F it would pretty much instantly convert to 'dry' steam, and could likely be recovered at about 10,000psi on the other side of the well.

It has been a long time since I had to figure out from a steam table how much energy was extractable from super heated steam, but it is a lot. It goes through the turbine, piped through a cooling tower to condense it back into water, and then dropped back into the source hole.

The risk of earthquakes and other geo-technical disturbances is minimized by what is essentially a closed loop system.

Now it is true that you're going to cool the crust (energy is conserved after all and if you're running turbines it means the crust is cooling) the question then is how quickly is that heat returned by other actions. And of course if you were to pull "all" the energy out fast enough this way you could presumably "freeze" the core of the Earth and that would be a bad thing, but we're talking about way more energy than the entire world consumes in a centuries and I'm not sure how to judge that risk compared to the heat generation mechanisms inside the planet. An actual geologist probably has an idea.