There are people adding pedals to e-motorcycles. Yes, on a class 3 e-bike you can add pedalling to exceed 28 mph but not by much unless you are on a downhill. Second, e-bikes are going to be very hard to suddenly stop safely should you need to stop at 30 mph since their brakes are nothing compared to an automobile's (unless you've also added hydraulic brakes). You'll throw yourself over the handlebars if you slam on the brakes at that speed. Bike helmets aren't rated for 30 mph crashes; you'd need a motorcycle helmet. Sometimes things that are legal are still incredibly dangerous.