It is a pity that only on POST Ext JS passes form parameters on submit. I propose that the code be changed that this happens when the method is not GET instead of method == POST as is currently the case.
The code is in Ext.form.Action.Submit and is really easy to change. I know that not all browsers function identically with PUT and DELETE, but if we wait for that to happen, no progress will ever made. For people who support only one browser, it is not really relevant if PUT and DELETE do not behave identically on another browser.
So please Ext JS team, consider transparent support for PUT and DELETE. You can even put in a disclaimer, but don't write code that make it impossible to use these methods.