I would admit that most open returns do allow BOJ, especially on the return journey. While technically the guard did their job by selling a new ticket, the way he went about it was not right - the self-gratification was entirely unnecessary, going on borderline arrogant and abusive, so I would definitely follow that up with TfW. If you bought it from a TVM and it didn't advise you to lookup the restrictions with the appropriate restriction code (in this case,
http://www.nationalrail.co.uk/8A), then I would also follow that up with TfW, and would politely ask to be recompensed for the fare paid as you weren't privy to the lack of BOJ restriction.
Out of course, I would personally follow it up with TheTrainLine, as if you previously saw the ticket on their app and made the decision to buy said ticket based on the information provided to you, then it could be argued that be a breach of contract/false advertising.