Yes, it would definitely have been lesser work to just use Cocoa. And yes one of the main reasons for choosing mobile web apps is that they are cross platform.

Having said that, I still applaud the guy taking the time and ploughing in so much effort into something that he wanted to do. I appreciate the true hacker spirit in striving to create a webapp that looks and feels totally native. Kudos to the OP.

Web apps also let you deploy changes instantly to 100% of your users as opposed to going through an app store update. That's huge. You have no idea how long users will take to update their apps.. and some never do.