From what I understand geothermal itself refers to heat of the earth (crust) while geothermal energy refers to energy generated within the earth mainly but not exclusive, nuclear decay. Calling ground heat geothermal is therefore correct, calling it geothermal energy is not. (see: https://education.nationalgeographic.org/resource/geothermal...)

What makes you think geothermal is only from nuclear decay? The core is hot because of the forces the moon puts on it as well.

Yea, there’s also leftover energy from the earth’s formation. Nuclear decay + moon + sun (tides and sunlight) + residual heat together all contribute to the amount of available energy.

Nothing. I used those words to distinguish from the other kind of shallow geothermal in nongeologically active areas.