Your question is a little unclear, but the
JSF form tag renders on the user's browser as an HTML FORM tag, and thus obeys the same rules as plain HTML. Which is that ONLY the data defined within that form will be sent when you submit the form. So if each tab has a JSF form on it, each tab should submit its data and only its data, not the data from outside the control or on any other tab. To submit all tabs from a single submit operation, you'd have to move the form tag to include the entire set of tabs.
There are ways to alter this behavior, but they're basically relying on you providing Javascript to dynamically add form fields as part of the submit process. Neither HTML nor the core JSF tagset have any options for that - you'd have to write your own.
The secret of how to be miserable is to constantly expect things are going to happen the way that they are "supposed" to happen.
You can have faith, which carries the understanding that you may be disappointed. Then there's being a willfully-blind idiot, which virtually guarantees it.