Are you stuck in 1980s? Nearly all large-scale software deployment has telemetry data on multitude of things. I know Hertz does because they use those telemetry data to tweak their UIs and such, to reduce human interaction time and increase productivity. They clearly have enough code to know if a vehicle is ICE or EV, and give the agent the option to pre-sell CPO for EVs instead of a tank of gas. The return process clearly has a subroutine for EVs as well. Let's assume this is a software bug but they have been renting EV for at least a year - how long is enough time to iron out these bugs? I actually think the return agent added this charge deliberately. When I raised this, the look on her face said it all - she was very surprised I caught it so fast and immediately removed the fuel line item after I pointed out what she did. If someone didn't do this on purpose, it would take some time to even understand what caused the discrepancy/overcharge.

I would submit that these could all just careless mistakes. However, the trend holds that this is not just random, I have had a lot of overcharges and if you had any experience dealing with these issues, you would know:
1) the issue can be fixed by the station before end of the day
2) if issue is not fixed and data transferred to Oklahoma, then station can't fix it and you have to call OK customer service line, which takes HOURS of hold time. Now the calls seem to be answered by foreign agents, so you have to content with language barrier
3) reality means it's easiest to have it fixed at the station, but they don't give you a receipt to look over.. and email receipts don't come within a few seconds like reservation emails. 9 out of 10 times, you wont' even know about it until you have left the city or past security with no way or not time to get back to the station.

If you put all these things together, you realize the deck is stacked against you, the customer. You have to ask yourself why!