Funny you should bring that up. As a matter of fact, the Society used to teach that urination and defecation would no longer be necessary once humans achieved perfection. Perfect bodies would completely use whatever nutrients were taken in and there would be no need for elimination. Somewhat along the lines of believing that blacks would all turn white as they approached perfection. Are you kiddin' me???
Like many of their other teachings (then and now), they were the products of a few jerks sitting around dreaming up their own ideas of how things "oughta be," without any Scriptural basis at all. So many of their earlier beliefs were idiotic and embarrassing, it's no wonder the Society discourages perusing older publications, or heaven forbid, the internet (!), and anybody who does so is automatically suspected of having apostate leanings.