makeWlhLink is a method for generating list items on special pages listing most wanted pages or similar. One can already overload the formatResult method in this class (it's public), but an extension developer may just want to tweak the link a little, without rewriting the entire formatResult method.

There is an actual use case in the AdvancedBacklinks extension, which adds special pages extending the WantedQueryPage class (you can see the class that would benefit from this here).