Most modern car ecu's let you set a top speed. The complicating factor is many are a one-way street, you can lower at will but there is no way to raise the limit without an expensive replacement ecu.I would have thought the rental agency would put on some limiter for liability reasons.
When I was about 20 YO a car dealership was forced to give me a replacement vehicle for a day or two because they made as service screw up. The only thing they had was a peppy looking convertible that took a while for them to have checked out for me. They obviously tweaked it into being a dog.
I pulled up next to two old biddies in an Austin Westminster at a light expecting to leave them in the dust. They beat me and weren't even trying.
As for old-school limiting, that was probably the same as kids snowmobiles. A throttle-stop or loose cable so you can't get full throttle.