SE
The phrase "confidential" is a legal term describing information that may effect the view an assessor has of a claimant, for example (possibly poor), the fact that the claimant is a compulsive gambler may not be relevant to their qualifying for ESA, but may unreasonably effect the Decision process.
Based on your post, I can't see any reason why the information you attached to your ESA50 would have been considered as such, the fact that you., as the claimant, attached it to your ESA50, would likely negate any claim to confidentiality.
Gordon
Nothing on this board constitutes legal advice - always consult a professional about specific problems