Assuming n isn't very large, I don't see why. People will spend sometimes days in on-site interviews. A simple coding challenge can tell you a lot about a developer and provide a shared basis for discussion in a subsequent interview. Of course "build a CMS from scratch" is ridiculous but simple simulated bug fixing and small feature additions that mimic real life work can be quite useful and not time consuming.
As someone who has spent a lot of time implementing & arguing for work sample based hiring, the hardest part is getting places to remove the useless interviews from their filter process.
Very few devs given the choice between 8 hours of interviews & 7 hours of work sample/1 hour of interview will choose the former. But companies just add the work sample & leave the interviews defeating the point.
