I don't know the answer, but the question works equally well flipped around. If they have it, why not release it? Hiding the information to ward of malicious actors and AWS competitors is security by obscurity, and not reliable. It's nearly impossible to hide a giant data center, so a dedicated person can track most of them down anyway.

I'd be more sympathetic if Amazon weren't holding a competition to see which city would give them the biggest tax breaks. It's only fair that everybody sees what other deals they're getting.