From Hikashop 2.3.4 stock update is based on "Invoice order statuses", but documentation and labels were not updated yet.
In Hikashop configuration, set "Update the product stock on confirmed status" to Yes, then set your Invoice order statuses.
If you use online payment, then set in your payment plugin option "Order status" to one of Invoice order statuses.
If you use bank transfer,wire transfer, collect on delivery..etc, set Order status to created and you have to update order manually when order is paid.