Those sound like "hiking definitions". They are wrong.
Class 1 = hiking. Including off trail hiking, screefields, whatever.
Class 2 = scrambling on rock but not requiring constant use of hands
Class 3 = constant use of hands, exposure, but easy enough a rope is not required
Class 4 = shortroping or simulclimbing terrain
Class 5 = technical climbing.
Class 3 and 4 overlap and both overlap with the lower end of Class 5. They are not exclusive definitions.