I am not sure if he was talking about use of subforms in HTML or in JSF. As he is asking this in the JSP forum and not in the JSF forum, I assume that he was looking for a HTML solution.
Well, the links you provided are for JSF only. If you want to achieve the same in HTML, just use Javascript to access the DOM and change the form action or change a hidden input parameter, indicating which button was pressed.
Like I said:
> just use Javascript to access the DOM and change the form action or change
> a hidden input parameter, indicating which button was pressed.
That is something like
document.yourFormName.action = 'page.jsp';
ordocument.getElementById('hiddenInputId').value = 'newvalue';