That’s not the case here though, we just have a topic and that’s about it, and this is why we wouldn't be getting the same stuff, how could you get the same stuff from a topic. It’s not like "paint a fruit bowl" type of situation here, it’s like "paint something regarding fruits" for example, would everyone paint a bowl of it in that case? Maybe one or two but I doubt it would be too many.
Have never seen the identical artwork submissions in these contest and why should we worry about the same if we are not copying someone else's work? You have something in mind and that cannot be same as in other's mind and you are right these are not classes where you have same object to paint on the paper.So be original and rest you don't need to worry at all.