Are we certain that Glacier is "geographically diverse storage."?

We know that to be true for S3 Standard. Even S3 Reduced Redundancy claims "The RRS option stores objects on multiple devices across multiple facilities".

But I haven't seen Amazon make a similar diversity claim for Glacier. Perhaps it's implied by the "durability of 99.999999999% of objects" claim they make? Hard to achieve that durability in a single data center if there's a non-zero probability of something like a fire or other catastrophe.