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

Notice the flash. I'd expect `suspended` to be `true` during the high pri render.
expect(renderer.toJSON().children).toEqual(['Loading']);
      scheduleUpdate(fiber); 
      expect(renderer.toJSON().children).toEqual(['Loading']);
      
      setSuspenseHandler(() => false);
      scheduleUpdate(fiber); 
      expect(renderer.toJSON().children).toEqual(['Done']);
      scheduleUpdate(fiber); 
      expect(renderer.toJSON().children).toEqual(['Done']);
      
      setSuspenseHandler(() => true);
      scheduleUpdate(fiber); 
      expect(renderer.toJSON().children).toEqual(['Loading']);
      
      setSuspenseHandler(() => false);
      scheduleUpdate(fiber); 
      expect(renderer.toJSON().children).toEqual(['Done']);
      
      setSuspenseHandler(f => f === fiber || f === fiber.alternate);
      scheduleUpdate(fiber); 
      expect(renderer.toJSON().children).toEqual(['Loading']);
      setSuspenseHandler(f => f !== fiber && f !== fiber.alternate);
      scheduleUpdate(fiber); 
      expect(renderer.toJSON().children).toEqual(['Done']);
    } else {
      expect(renderer.toJSON().children).toEqual(['Done']);
    }
  });
});