Recently off the Eurodam. Had a small amount of non-refundable OBC (we used most of it for tips) and wanted to test if it would be applied to the balance (from our casino visits). At first (after leaving the ship) HAL did that, but then a couple of days later they reversed it and our final bill was a bit higher.
Thus, HAL is paying attention to the refundable and non-refundable balances, at least on the Eurodam.