Mediocre rating and imposter syndrome but excelled in selling themselves? I don’t feel like this is the full story. What is the purpose of this ask? To receive validation and an excuse to go against some self perceived principles? If you look to let them go do it without requests for psychological support or pursuit of excuses. You are a human too and you deserve support, but in this situation, the other party will need more of it and possibly bears less responsibility for the outcome.