You’re misinterpreting the law.
Florida
statute 320.01(42) defines a “Low-speed vehicle” as any four-wheeled electric vehicle whose top speed is greater than 20 miles per hour but not greater than 25 miles per hour, including neighborhood electric vehicles. And any LSV needs to have certain safety equipment and be registered. In order to register an LSV, it’s got to have a VIN and carry the expensive PIP insurance.
Nowhere does it say that a vehicle with a VIN must be registered.
If you downgrade the motor/controller to make it incapable of exceeding 20 mph, it no longer meets the primary definition of an LSV but instead meets the definition of a “golf cart” as designated in statute 320.01(42).
Conversely, if you upgrade a standard golf cart motor to exceed 20 mph they can and to issue you a very expensive citation for “driving and unregistered motor vehicle” even if the cart ha no VIN.