Don't judge them too harshly. I am currently developing web app with offline capabilities. FT which provide the scaffolding code recommend using the cache manifest only for the absolutely minimum requirements (jquery + 10 lines of html) and use local storage for all the rest.
Admittedly, when I was working on it, we were trying to wrangle it into something it really wasn't meant to do, but that fact - that it wasn't a good fit for our application - wasn't at all obvious until I finally started encountering all the "gotchas", and reading more about them.
I suppose they know what they are talking about.