I do wonder whether BA deliberately trains its staff to mislead customers like this, or perhaps they just don't train them and let them make it up as they go along.
It must surely have been obvious from the booking records that due to failure of BA equipment the passenger arrived at destination 17 hours late?
The re-routing (and the apparent 'generosity' of the airline in preventing an even longer delay) is neither here nor there.
Maybe the publishers of the Idiot's Guide series of books could produce an 'Idiot's Guide to EC261' - it should sell in bulk in BA and a few other airlines as well.