It's not necessarily a conventional motor, even - many simple riding emulators just use a brake.
A more intelligent or interactive one is probably using an alternator or dynamo, which can be gently driver to overcome friction when needed to simulate coasting.
It could be a BDLC style, but the majority of the time it's acting as a generator and load dumping system, not being electrically driven as with a normal motor.
I'd expect something with either many more poles than a typical BDLC servo, or a higher resolution encoder for smoother current control - not just a simple three switch hall setup, as commonly used.
Or it could even have a combination of electrically controlled friction brake and a small "coasting" motor, to avoid any notching due to commutation?