They have to offer a guarantee since most of their business is mail-order and the biggest concern is if you'll be able to ride the durn thing at all because of the moving bottom bracket design. The whole drive train is on a swivel. I'm aware of ONE owner in my area, and he's had it over a year and is still afraid of riding it. For some reason, most people with this issue simply re-sell them; and obviously the ones who like them keep them.
BTW, this is purely of recumbent interest, should not be in the General Cycling forum.