Brendan,
even simple things like an outside tap, €50/80, are often agreed and paid for at this stage and the builder gets paid up front. Small beer maybe but buyers (like I did) don't want their new homes as building sites once they move in and get this done and dusted as early as possible.
My point always has been that this "Sale Agreed" rubbish bestows some mythical protection in the minds of buyers that does not exist in law, particularly in the minds of young, first-time buyers which it seems some of the disappointed parties are in the example I used.