No - if you read again: hidden variables for View state, not Session state.
Put simply how to preserve the state of a complex form, while dealing with validation, perhaps a form of multiple pages (e.g. flight booking).
>>> The hidden fields are used prior to validation. <<<
If you're keeping this information in memory or some kind of session store between requests, you're doing things badly wrong and will end up with a) alot of junk in memory for users that didnt come back and b) a whole load of extra processing as you have to re-validate the data on every request until the form is finally complete and c) a whole load of extra complexity in your code to deal with.
Jeez - this is basic stuff that people learnt with CGI ten years ago.