Why no onFieldsChange in FormInstance?

It is very limiting to have onFieldsChange only on <Form> instead of on FormInstance. I would like to be able to add a listener to form so other components can react to fields changing.

My current use case is automatically disabling the buttons in <Modal> if no fields are dirty:

/** 
 * Don't want to repeat logic over and over, want one Modal component that automatically
 * changes ok/cancel buttons based on form state
 */
function MyFormModal() {
	const [form] = Form.useForm()
	return (
		<Modal form={form} visible>
			<Form form={form}>
				...
			</Form>
		</Modal>
	)
}

// disable okButton if dirty
// only show cancelButton if dirty
const Modal = ({form, onFinish, ...props}) => {
	const [dirty, setDirty] = useState(false)
	if(form) {
                 // Really need this!!
		form.onFieldsChange(() => {
			setDirty(form.isFieldTouched())
		})
	}
	const buttonsProps = {
		cancelButtonProps: dirty ? cancelButtonProps : {...cancelButtonProps, style: {display: 'none'}},
		okButtonProps: dirty ? okButtonProps : {...okButtonProps, disabled: true}
	}
	return <AntModal {buttonsProps} {...props}/>
}

How can I achieve this currently?

The issue identifies FormInstance and

as the relevant entry points; start by reading their current field-change APIs and subscription behavior. Clarify listener lifecycle and dirty-state behavior from the modal example. Done means a FormInstance listener can observe field changes reliably and the behavior is covered by tests.