It isn't pedantry. Expressing a wish that something "could" be done is ambiguous. "Could" is both used as you originally intended and as an expression of ability. It's not pedantry to misunderstand, and it's not pedantry for GP to explain why the misunderstanding occurred.
A misunderstanding occurred. The misunderstanding was clarified, acknowledged, and explained. I'm not sure it contributes anything to make accusations of pedantry.
A misunderstanding occurred. The misunderstanding was clarified, acknowledged, and explained. I'm not sure it contributes anything to make accusations of pedantry.