The articles I have read say a lot of the Tesla's are high miles - like closing in on 100K. Thats a lot of miles for any rental. I would look at it differently, it cost Hertz some money, for which they got a lot of free publicity and some new customers possibly. Now there attempt has been determined to not be great, so there adjusting there business model.
I wouldn't own or rent a EV. No interest. But I don't think in the end Hertz is out much. I would say it does however reflect poorly on the EV manufacturers - given this was a fairly broad test that proved to be not lucrative for a rental company, and hence might similarly make it a poor choice for a private citizen dependent on their usage.