Technically its passing 'a list -> 'a list, and only becoming an int array because thats the final input value. The fsharp functions are closer to the C# functions Func<List<IComparable>, List<IComparable>>

Or to be even more pedantic it's

Func<T[], T[]> where T : IComparable<T>

But maybe all of that is just stronger arguments for F#'s inferred typing...

Or to be even mooooooore pedantic the fsharp functions would probably be written to be seq<'a> -> seq<'a>, so that would be Func<IEnumerable<T>, IEnumerable<T>> where T : IComparable<T> :)

I think I just tried to say that I didn't specifically intend to write very verbose C# to make a point. I tried to write good real world production C# and then compare it to how I have seen people do DI in real world F#, which is partial application in this case. There is other ways of doing it too, but this is the most common pattern I've seen.