I think most of the problem with the statement is that it is ambiguous. If she is saying that the Gaussian distribution is used because it assumes there exists people who are the mean average representatives of humanity; then she is just failing to understand what the law of large numbers implies about the distribution of sample mean(X) regardless of the distribution of X.

If on the other hand she is saying that a problem in healthcare is that significantly different sub-populations are lumped together resulting in inappropriate benchmarks for some sub-populations, that is more palatable. Even if this latter interpretation is not true, at least it isn't false by definition.