It would make sense what you are describing. In summer the water you see by the wheel well is condensate from the cooling process, similar to what you see from a home HVAC central A/C unit.
The process of a heat pump basically reverses the evaporator process where the heat is channeled to the living area evaporator rather than cool when in A/C mode.
When in heat pump mode, the inside evap coils are warm, so the pan inside will not see much condensate, if any to be discharged in the location by the wheel wells. However, in fall when in heat pump mode, the outside evap coils discharge the cool air and it is entirely possible and probable that you'd see moisture coming off the outside coils in certain circumstances in heat pump mode. Keep in mind from what I understand there really are not pans, hoses or drains for the outside evap coils, so condensation coming off the roof should be expected.
I think what you are seeing is perfectly normal.