Easy enough to demonstrate if you have a fresh snake skin. It should feel kind of wet, kind of sticky, kind of slimy. Those are the oils they produce to aid in shedding - bathing simply washes all of that away.
Snakes don't need a rough surface to shed. It makes the task a bit easier if they have one but they will find a way out of that old skin regardless. If your friend just provided proper humidity instead of soaking she'd probably get those whole sheds more often.