Maybe I'm missing something as a newbie but who cares if there is a lite coat of lead oxide on the balls? What's the down side if you leave it on from a performance perspective?
Are there any potential health issues with handling balls with powdered lead oxide on them from an exposure perspective? Lead exposure isn't anything to take lightly.
Well, lead oxide crumbles into powder very easily, making airborne lead contamination a more serious consideration when handling. Shooting oxidized bullets may also result in higher airborne lead levels in the area.
Of course, how much of a concern this is depends on the amount of oxidation present.
So if you clean the oxide off lead bullets, appropriate care must be taken to minimize/prevent either inhaling the dust or spreading the dust to other areas, creating a lead contamination concern that can later be either spread airborne or ingested through handling.
Oxidized lead bullets "swell" somewhat, too, as the layers of lead oxidize. Anybody who has, for example, had an old box of lead (unjacketed) .22 ammunition that has partially oxidized can tell you that they can be quite the snug fit when inserting into a cylinder or chamber.
Removing the oxide layer down to bare lead again reduces the diameter of the bullet. This may or may not be much of a concern, depending on the amount of removed material and the type of bullet. Ball ammunition for muzzle loaders, for example, would be a lesser concern since these are patched when loading.
However, removing the lead oxide also changes the size, mass, and potentially the shape of the bullet due to several factors, the two most important of which are amount and uniformity of oxidation as well as how the oxide layer is removed. All of this can adversely affect the ballistics of the bullet.