Can you this give a look please?
Adding any type of button to the header breaks the layout: http://jsfiddle.net/MauriceG/veTtY/
Header Buttons: Support submit, reset, and input buttons in header to…
When I added "button" to that selector to fix #4638 I have been thinking about adding form buttons as well.
I decided not to do that because the function looks for immediate children and input type buttons are supposed to be wrapped in a form element.
So it would only aply if the page (data-role="page") itself is the form element and the header contains an input button. I think we are looking at an edge case and wasn't sure if it has negative impact on performance.
People still can get the same styling by adding class ui-btn-left/right to the markup.
As discussed on IRC we close this for now.