useImperativeHandle have bug in 16.8.1 if you want to access any state will get the initial state not current state but in 16.8.0-alpha.1 it work good 

You can see here https://codesandbox.io/s/xjl8znwpz open console when you change input value will get the currently value in console but if you clicked button get value from ref will get initial value (e)

If you try same here https://codesandbox.io/s/qxkll6po0j with 16.8.0-alpha.1 when clicked button get currently value

/**
 * Copyright (c) 2013-present, Facebook, Inc.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 * @emails react-core
 * @jest-environment node
 */
'use strict';
let React;
let ReactFeatureFlags;
let ReactNoop;
let SchedulerTracing;
let useState;
let useReducer;
let useEffect;
let useLayoutEffect;
let useCallback;
let useMemo;
let useRef;
let useImperativeHandle;
let forwardRef;
let memo;
let act;