UL testing and listing costs money and takes time. for an e-bike i would assume they have verified wire sizes, terminations, etc on various components and motors to ensure that everything is sized properly. UL and non UL listed product may very well be the same or it might be a the cost of a single component. UL listed, UL certified, UL recognized, UL rated all mean something different and it has been awhile since i've been in the weeds on UL.
UL listing is not required, but most reputable manufactures, suppliers, vendors, etc (as well as their insurance company) require products to be UL listed/certified. Very questionable for a vendor to offer a choice. I'd look for a different vendor and manufacturer.