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

Notice the flash. I'd expect `suspended` to be `true` during the high pri render.
expect(ReactNoop.getChildren()).toEqual([span('A')]);
      
      await ReactNoop.act(async () => {
        React.unstable_withSuspenseConfig(
          () => transitionToPage('B'),
          SUSPENSE_CONFIG,
        );
        expect(Scheduler).toFlushAndYield(['Suspend! [B]', 'Loading...']);
        Scheduler.unstable_advanceTime(1000);
        await advanceTimers(1000);
        
        expect(ReactNoop.getChildren()).toEqual([span('A')]);
        Scheduler.unstable_advanceTime(1100);
        await advanceTimers(1100);
        
        expect(ReactNoop.getChildren()).toEqual([
          hiddenSpan('A'),
          span('Loading...'),
        ]);
      });
      
      Scheduler.unstable_advanceTime(3000);
      await advanceTimers(3000);
      expect(Scheduler).toHaveYielded(['Promise resolved [B]']);
      expect(Scheduler).toFlushAndYield(['B']);
      expect(ReactNoop.getChildren()).toEqual([span('B')]);
    });
    it('classes', async () => {
      let transitionToPage;
      class App extends React.Component {