Trying this test case:
<h:commandButton id="submit" value="Submit">
<f:param name="someparam" value="123"/>
<f:ajax .... />
The final link appends the submit script, but it should not. In theory the submit script should be added but in practice there is no clean way to detect if a "submit" behavior has been added to the component, so to keep things simple, if the button is submit type, it is responsibility of the developer to add a client behavior that submit the form, for example using a f:ajax tag.
Otherwise, there will be a situation where a full submit could be trigger after an ajax operation. Note we still need to append two scripts if necessary: autoscroll and clearhidden fields, because this code is called for a submit button.