Yes but calculating the energy draw required for any measurable change in this effect is very different from knowing the rough process it operates on.

We know how weather works quite well, but knowing if it will rain in a week is an entirely different beast.

I've seen a confident estimate in the form of a calculation. They know what kind of compounds (term?) are in the outer core and they know the minimum temperature those compounds need to be at to be free-flowing enough to sustain the field. And I'm pretty sure we know the current temperature of the outer core.

My memory is that the calculation found that if humanity switched to geothermal for all its energy needs, then in only about 1000 years, the core cools enough for the magnetic field to stop, but I am not sure.

(We should definitely deploy geothermal in the Yellowstone caldera though long enough to cool it down enough so that it will not erupt again.)

That is definitely not true hahaha. The outer core is several thousand km down, and the crust is only 30km thick. And we have the entire mantle below us.

Humanity could max out geothermal for a million years and never make a dent.

Whoa, this is a bit scary. As mentioned earlier, it should basically be used in a way where other energy sources are tapped first, and only the shortfall is covered.