You could replicate this functionality using a field within the form:
Some field: SubmitBool.
once the form has reached a state that a submission would be appropriate set the SubmitBool value to true, and have rules change behavior once the value has changed.
You could also do something along the lines of having a form status field,
ie: Status = Open/Draft and change upon submit.
You can hide buttons to submit based on the value of that field.
Another thing to check is that you are using the same value for the file name upon submit. If you are appending a date to the file name and set it at form load without checking if it has already been set, it will save the form as a new file.