I agree with thor that 30kg seems like a very heavy touring load. I may occasionally carry that much for the few miles home from the grocery store but it would be unusually heavy. My touring load is generally under 10 kg.

The nominal weight limit is going to be a rough guideline since there will be lots of individual variation. A rider who jumps curbs, frequently rides fast over rough roads, and/or has a strong mashing pedal style will put much more stress on the bike than someone with a smooth pedal style who rides on smooth surfaces and is careful to steer around potholes. So the latter type of rider may well exceed the nominal weight limit without any problems while the former type could be under the limit but experience repeated mechanical failures.