Perhaps the reason they need to recharge in descent is less to save energy for the next flight, but more the need to have reasonably well charged batteries in c

Perhaps the reason they need to recharge in descent is less to save energy for the next flight, but more the need to have reasonably well charged batteries in case they need to perform a go-around. Rate of climb when the batteries are discharged is likely to be pretty low. So maybe they will need to operate the turbine at full power while descending to achieve this, whereas normally the engines on a turboprop would be nearer idle in the descent.