In the first example the named interface would be easier for me to read in a large project than Func<List<int>, List<int>> and with actual code there for implem

In the first example the named interface would be easier for me to read in a large project than Func<List<int>, List<int>> and with actual code there for implementation the two lines to define the interface would end up being a tiny fraction of the total lines of code. An interface would also provide better documentation opportunities for someone trying to write a mock or new implementation. The code in the article isn't outlandish or particularly verbose.