It's description says it's for flatwater up to class III, I'd imagine once you have some moving water experience and some practice on class II you could take it down class III without getting dumped.
Just because the boat is rated for up to class III doesn't mean it is an auto-pilot for your next river trip, you're still the captain and have to navigate it.
Make sure you square up to waves/holes - hitting them sideways will always dump you in a ducky.
People run class III and IV on SUP boards now so I'd say yes, it really will do class III.
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