Honestly this might be a bad opinion and ideally you should email grad rec but I would selfishly attend the ac (only because this process is so hard and DBP is a great firm)😭😭😭. The grad rec should have spotted this in your application and it’s not your fault (but why did you apply in the wrong year?😭).
Like even if you attend the ac and are successful and do the vac scheme and worst case scenario, they realise their mistake and don’t offer you a tc, atleast you have a great firm vs experience on your cv😭. Best case scenario, maybe they noted this and think it won’t be an issue? Or they defer your tc offer to the next year should you be successful in getting one?
Guys pls don’t attack me, I know it’s bad and unethical advice but this person has worked hard and made it so far in the process and it would be so sad for them to lose it😭😭
Best of luck anyways!