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

Notice the flash. I'd expect `suspended` to be `true` during the high pri render.
let setShouldSuspend;
      function App() {
        const [shouldSuspend, _setShouldSuspend] = React.useState(0);
        setShouldSuspend = _setShouldSuspend;
        return (
          <Suspense fallback="Loading...">
            <Child shouldSuspend={shouldSuspend} />
          </Suspense>
        );
      }
      function Child({shouldSuspend}) {
        if (shouldSuspend) {
          throw never;
        }
        React.useEffect(() => {
          Scheduler.unstable_yieldValue('Mount');
          return () => {
            Scheduler.unstable_yieldValue('Unmount');
          };
        }, []);
        return 'Child';
      }
      const root = ReactNoop.createLegacyRoot(null);
      await ReactNoop.act(async () => {
        root.render(<App />);
      });