When does VuGen record a web_submit_data instead of a web_submit_form? Why? (Be as specific as possible)

A web_submit_data is recorded when VuGen cannot match the action, method, data fields, and/or hidden data values with the page that is stored in the record proxy cache. Comparison failures are typically caused by something other than HTML setting the properties of the HTTP request. Because VuGen can parse only HTML, it cannot find all the properties of the HTTP request in memory. This results in the hard-coding of all the request information in a web_submit_data statement.