@edpmay, yeah I see what you’re saying. Your reasoning makes sense to me for a theoretical system (adiabatic duct boundaries so no ambient waste heat loss, discounting mechanical work done by fans to move air through ducts - which I believe is discounted in ideal air loads anyway), not sure why it wouldn’t work. HB calculates mechanical ventilation by subtracting the energy from the supply coil for that zone, from the zone energy [2].
I agree with @MingboPeng that there may be some intricacies in the HB ideal air loads implementation that might be creating unknown side-effects to mitigate the heat recovery.