I actually have the opposite take - I've seen "the Amazon HQ is definitely at <place>" reported so many times, with different places, that I won't believe that they're actually putting it there until the electricity is on, people are commuting to it, and they have a contract with a landscaping firm.
I think "HQ" is an intentionally overloaded term, and what will eventually happen is that Amazon will build something in most of these locations, constantly fighting against ballooning budgets typical with massive infrastructure projects