My website gets visited at least once a day or so from IPs that give Amazon AWS domains for reverse DNS requests. The User-Agent strings are those of browsers, not bots. Could these be real people, or are they bots spoofing the UA?
Tough to say without more information, but possibilities you mentioned are likely. They could also be using a VPN and have a DynDNS setup using AWS maybe?
If you check the user behavior and see if it matches up with bot traffic or user traffic. And you could also check the hostname.
Interesting question, but to my way of thinking no matter what the answer is it isn't going to change anything you are doing in terms of work.