This DEV-only field was added in 836331ba5f69f2cc53b273ec073fae116db14302 by @sebmarkbage but it's not being used anymore to my knowledge.
primaryChildFragment.memoizedState = mountSuspenseOffscreenState(
        renderLanes,
      );
      workInProgress.memoizedState = SUSPENDED_MARKER;
      
      
      
      
      
      
      
      
      workInProgress.lanes = SomeRetryLane;
      return fallbackFragment;
    } else {
      return mountSuspensePrimaryChildren(
        workInProgress,
        nextPrimaryChildren,
        renderLanes,
      );
    }
  } else {
    
    
    
    const prevState: null | SuspenseState = current.memoizedState;
    if (prevState !== null) {
      
      
      if (enableSuspenseServerRenderer) {