This also ignores that the Earth already has a flux of 50TW per year, so it's only an increase of about 40% (and even less, when you consider that intentional extraction would slow the flux of all surface area above it).
Not only that, but Earth's internal heat is being renewed constantly via things like radioactive isotopes and tidal forces.
So what happens if we slow that flux? That's spread across the globe. What's the impact if those numbers are localized?
Radioactivity and tidal forces create a fixed amount a heat and that heat dissipates at a given rate, right? So what happens if we change that rate of dissipation/extraction?
The point is, it's all handwavy. Seems familiar to just about everything we've done before - fossil fuels, plastics, PFAS...
Not only that, but Earth's internal heat is being renewed constantly via things like radioactive isotopes and tidal forces.