Hi John,
The main confusuon seems to be that when travelling to a dual zoned station it is treated as being in the zone relevant to where you’ve come from. In this case that is zone 2. Travelling in the afternoon peak with a railcard is one of the cases where Oyster isn’t always cheaper, especially if you don’t finish in zone 1.
The National Rail Enquiries site is definitely wrong on this. Whilst it’s good that they now seem to be defaulting to PAYG fares rather than paper ticket fares in the contactless area, they do need to get it right. I’d be interested to know what response you get from them.
As to being offered the cheaper discounted Anytime Return fare, that is simply not possible when using Oyster or contactless PAYG. If you had gone to the ticket office at Vauxhall then that is exactly what they would have sold you.
Sorry I don’t have better news, but you have been charged correctly.