Redux-persist How to reset state of sub key in state

Hello I have a redux store with nested state and multiple reducers such as :

{
    user: {
        username: “UserOne”
    }
    content: {
        data: “”,
        isFetching:true
    }
}

I want to ensure that when the user refreshes the app (CTRL + R) , all state is persisted except isFetching which should reset to false. I have set up my redux store with a persistor as follows to try to achieve this:

const persistingReducer = createBlacklistFilter('content', ['content.isFetching']);
const persistConfig = {
    key: 'root',
    transforms: [persistingReducer],
    // Refer to migrations file for versions
    version: 20210426,
    storage,
    stateReconciler: autoMergeLevel2,
    migrate: createMigrate(migrations, { debug: true })
};

const reducers = combineReducers({
    content,
    user
});

const rootReducer = (state: Store | undefined, action: Action) => {
    if (action.type === USER_LOGOUT) {
        state = undefined;
        console.log('Logged out. Store reset.');
    }

    return reducers(state, action);
};

export default persistReducer(persistConfig, rootReducer);

However, the isFetching property still remains true after refresh. Anyone have any idea why.