This is an SSO for ID purposes. (passport/national ID).

Central repository won't store anything, the same as google SSO doesn't store your data if you sign in to third party sites. (it just authenticates you).

Maybe this is what you are misunderstanding?

Also, government already has your data, so that 1 central repository for IDs already exists.

As for hacking... going after any one of those 3000 is less likely to get you in trouble then going after a government (as incompetent as they are). See oil pipeline hack to understand consequences.