I don't know about that. The fleet dump strategy made it very cheap for the rental car companies to churn their cars quickly, dumping a lot of low mileage cars onto the used market for low price. Obviously if there's a glut of 1 year old cars on the lots, that's obviously going to lower the price of the 3 year old ones. Particularly if they are all similar models (eg GM W cars).And dumping them in such large numbers on the used market doesn't hurt them either. The Camry isn't just the most popular new car, it's also one of the most popular used cars. So it's not like having a certain model flooding used car lots hurts a car's sales potential. Having a lot flooded with sloppy unappealing midsize sedans does.
Now that the dumping era is over, it seems like the rental car companies are keeping them longer and running them into the ground.