It's possible that Honda's recommendation is because of the possible situation that the vehicle has been running on battery for the last part of its journey resulting in the battery having a low state of charge (and thus vulnerable to deterioration) before it gets parked. I'd love to know if the nominal 1kWh battery, which has to survive heavy charging and discharging, is actually a much higher capacity battery configured to operate in the middle of its charge range. Then, as the battery wears, it progressive encroaches on the unused part of the charge range in order to maintain the working capacity.