Change unit price on open order line with some shipped releases

We are currently doing a pricing update exercise and price lists and updating of part prices works good using DMT to import. I have one scenario I need some guidance on. We are have some open sales order lines which have multiple releases due over a number of different dates. In this scenario we want to update the price on any open orders on 1st February. The question I have is that we have orders with a line with for example 5 releases, where 2 have already been shipped and invoiced. I have been playing about in test and if I update the unit price, the full order line value increases.

The existing posted invoices remain unchanged, so my question is whether the new order line value actually has any real impact on anything, particularly financial transactions.