I guess there's some benefit of requiring more stability. But as others have already said, it's such an unbalanced, potentially unsafe exercise that you're unlikely to get any other benefit from it because you can't load it up much (either because of technique failure or because of removing half the strength of your back/arms), and frankly there's much better exercises out there for stability purposes. I'd be more likely to recommended 1-legged deadlifts than 1-armed deadlifts, because then at least your limitations are going to be more closely related to what your legs can lift than what one arm can support in an awkward position.
ETA: I'm also not a fan of the 1-arm clean, or even just DB cleans. It seems to me that the use of the bar in both hands more readily promotes the action on pulling yourself under the bar, whereas these modifications make that harder to do. You might see that as justification for making the modification, but the way I see it, the complexity of power cleans is a requirement to ensure that it is the power of the legs transmitted through the body moving the weight, rather than using the strength of the arms to get the bar up. Further complicating the movement seems like it would only make it harder to actually achieve the desired result, in my opinion.
