Yup, I did this every year when I was going to the states for 3-4 weeks in summer. I started booking in January, then about every week I checked the price for the same summer date, in general it was cheaper so I cancelled/rebooked, multiple times.
Also instead of rent from airport, I rent from smaller places (that handle Hertz/Enterprise/National/etc) and I always booked a subcompact, and 50% of the time they had none and gave me a compact/full size car. I had multiple Yaris yes, but one time I got a Dodge Caravan, a Fusion Sport V6, a Flex, a Jetta, a Soul, etc.
Similar happened to me, I booked a gas car but received a hybrid instead.
I'm curious, what's the advantage of renting not from the airport? I prefer the airport because it's easy to locate, especially when the airport is new and I'm dizzy after long flights
If you really are dizzy after a long flight, you probably shouldn't be driving, especially in an unfamiliar car in an unfamiliar area. Maybe you were just being hyperbolic about the dizziness, but people can make the same kinds of mistakes driving while sleep deprived as while driving intoxicated.