I wouldn't recommend trying it because of the amount of problems I've seen it cause with hamsters.
With hamsters (who pouch bedding), it can become lodged in their pouches or painfully block their digestive system if accidentally ingested. Another problem is it becoming tangled around teeth or trapping limbs causing circulation to be cut. In the worst cases of the latter, hamsters have been known to gnaw off their own limbs to free them and even died from blood loss. If they're lucky, the limbs may have to be amputated by a vet.
This is problems that occur with using bedding like this with hamsters, so it would put me off even trying it with piggies.
The adopters are much better off using a safe bedding like Fitch or fleece or hay. If they really wanted to use cotton balls, then they could use either ripped up white unscented toilet paper or pet shop equivalent.