Since babies and toddlers wear diapers 24 hours a day 7 days a week and use only diapers and no toilet for both urination and poop then I would see no way of someone becoming incontinent while wearing diapers instead of using the toilet.
If that were true of becoming incontinent from wearing and wetting diapers 24/7 then it would be impossible for a baby or toddler to stop wearing diapers since they would need diapers to keep from wetting their pants and they wouldn't be able to get to the toilet in time to urinate there instead of the diaper.