East London Line Launch on Sunday 23rd May.
I've encountered this issue too. The chap at London Bridge told me it is a deliberate part of the Oyster system as adopted by the rail companies - it is designed to stop those people wishing to pull a fast one i.e by touching in and out at the same station then boarding a train to an un-manned station and travelling for free.And did I mention that if you touch in and then touch out at the same station (e.g. because your train is cancelled and it's quicker to go home another way), you end up being charged a maximum fare because the Oyster system is confused?
In other words when you enter a station, then exit it, you're treated by the rail companies as if you were going to evade payment.
Therefore, If you enter a rail station and change your mind (or more likely the trains are cancelled/delayed) as far as the train companies are concerned you have to go through the refund system and beg for your money back.
Yet another reason why I shall be keeping my paper season ticket.