Howdy in my opinion hydronics and geo are two different systems. hydronics is what you would apply on your baseboard heaters, Boiler to heat water and pump to circulate hot water.
Geo has Heat pump with, if ordered hot water for domestic hot water. through loop inside unit that hot gas from compressor heats, besides it`s other operation is to heat the air and blow into ductwork. Or cool depending what owner has selected at stat. But hot water is generated heat or cool.