When call 'load' method to load form data, all the form fields will be validated. It is a way to indicate user if the data is valid.
You can write some code in 'onSubmit' event to determine if the form can be submitted.
$('#f').form('submit',{
onSubmit:function(){
return $(this).form('validate'); // prevent invalid data to be submitted
},
success:function(){
//...
}
});