Correct, fragments are per site, since we wanted to give site admins (or web developers working on a specific site) the flexibility to create their fragments without needing someone with global permissions.If you want to create fragments that are available in all sites, you can do that by including them in a deployable module (docs for this should be available this week). These fragments will also be automatically propagated when redeployed, which I believed you've also asked for in other posts.
