Some years ago I seen a new build home fitted with a GSHP which heated a large UFH area in a residential property.
The hot water was provided with an unvented cylinder that had a separate smaller heat pump integrated with the cylinder.

The collector for this heat pump was the UFH circuit.
Do systems like this require the main heat pump to operate in tandem with the hot water heat pump?
So that the system is providing a 2 stage temperature lift to the hot water cylinder?

Also could anyone name any companies using this method?
Many Thanks.