Hello,
Sorry for the delay.
It seems refunded items are more complex than I thought.
If you refund the main order totally, it will change the main order status to “refunded”, which will make the suborders “refunded” as well.
If you go to the main order and refund it just partially, WooCommerce itself will not change the main order status. It will keep the same status, thus the suborder status won’t change either.
Now, if you try to refund a suborder clicking on the suborder page directly, and not the main order, it will change its status to refunded, and then it will reflect its status on the main order. But you would have to refund it completely, not partially.
Would it be enough for you?