Ground-source heat pumps (with a few exceptions and borderline cases like those mentioned in the article) are not sources of heat, so you can only "get heat from" them in the short term; as with a battery or an interest-free checking account, though you may be able to temporarily run a debit balance, in the long run you can only get out what you put in.

This is a fundamental difference from energy sources.

Energy storage is an important complement to energy sources, especially renewables, and can substitute for energy sources to a limited extent, but confusing them is a fatal error.