Repro: https://codesandbox.io/s/fast-water-4i4jb

Notice the flash. I'd expect `suspended` to be `true` during the high pri render.
await advanceTimers(10000);
    expect(Scheduler).toHaveYielded(['Promise resolved [Async]']);
    expect(Scheduler).toFlushAndYield(['Async']);
    expect(ReactNoop.getChildren()).toEqual([span('Async'), span('Sync')]);
  });
  it('switches to an inner fallback after suspending for a while', async () => {
    
    ReactNoop.expire(200);
    ReactNoop.render(
      <Fragment>
        <Text text="Sync" />
        <Suspense fallback={<Text text="Loading outer..." />}>
          <AsyncText text="Outer content" ms={300} />
          <Suspense fallback={<Text text="Loading inner..." />}>
            <AsyncText text="Inner content" ms={1000} />
          </Suspense>
        </Suspense>
      </Fragment>,
    );
    expect(Scheduler).toFlushAndYield([
      'Sync',
      
      'Suspend! [Outer content]',
      'Suspend! [Inner content]',
      'Loading inner...',
      'Loading outer...',
    ]);
    
    expect(ReactNoop.getChildren()).toEqual([