Mathematics models data, and you can't model without assumptions. It's like developing a theory which can't have axioms. For example, kernel regression probabilistic model is a terrible model (assumption) with very large error for a large class of distributions[2], and so on. We're talking about picking the best technique; this technique is going to pick some assumptions arbitrarily that will or will not work well based on an unclear choice of the organizers. That's why I would prefer if they stated instead "Functions with some real world relevance", or "Typical functions", or maybe "Poorly behaved functions", and so on.
[1] http://en.wikipedia.org/wiki/No_free_lunch_in_search_and_opt...
[2] On the wikipedia page you can see they do make assumptions on f to minimize the squared error for choosing the kernel. It's inevitable.