It is excessive to claim that code cannot express the "why". You can almost always express the "why" with code if you really want to, though whether or not that's a good idea is another matter.

For example, you could express the same information that the comment in your example provides in the following manner with self-documenting code.

    enum PerformancePrioritization {
      FastWorstCase,
      FastAverageCase
    }

    function sort(data: List<TypeOfData>, performancePrioritization: PerformancePrioritization) {
      if (performancePrioritization == FastWorstCase) {
        heapsort(data);
      } else {
        quicksort(data);
      }
    }

    ...

    sort(data, FastWorstCase);