There likely is greenwashing. The percentage of their fleet consisting of EVs is likely small. Most modern ICE vehicles only need service every 10K miles on their ICE components. This may amount to $1000 for the time rental companies are operating a particular vehicle, a fraction of the overall revenue.

Alternatively, how are rental companies charging returned EVs? The time spent sitting at a charger should be considered as lost revenue when an EV comes back empty.