Well, for sake of absolute purity the minimums and maximums might be better placed in the Statistics modules, too. It's a little late to make that decision pragmatically, since L::U is standard and already includes them.
Where to draw the line on what to include and what not to include can be a difficult one. Second-guessing the maintainer about what they are willing to maintain and not maintain according to their vision for the module doesn't seem very productive. If someone has a clear and sensible argument for additional functionality, then I'm sure it would be considered along with other factors.
It would take quite an argument, I think, to argue adding functionality to a core Perl module that already exists in multiple CPAN modules. One would have to convince the maintainer that the additional code is ultimately useful. It would have to meet a common need. It can't spread development and testing time too thin. It can't bloat the core distribution too much. Any additional functionality has to fit with the theme of the module as understood by the maintainer. Ideally, someone wanting additional functionality would present a well-suited patch in the style of the existing code along with an argument covering each of these points.
There's still not a guarantee what the maintainer of a module will agree to do. After all, that person or team has to maintain those changes even if they accept the patch. It would go much farther than just saying essentially "I can foresee other operations on lists, and all of them should be in a module called List::Utils".