That's just evidence that multiple humans share the same account for whatever reason.

My guess on how it's happening is that Amazon Turk workers are presented with tweets and then they select from a list of machine-generated responses. I'd still call those bots.

I think it's more likely they all use shared computers and one person didn't log out of their account. The same way Ted Cruz's account liked a porn tweet about some incest porn, media guy (because as much as I love the idea of Ted f*ing Cruz trolling twitter for some porn I doubt the man runs his own twitter) forgot to log out of the account he was managing, is probably how we got this multi-aged meta human.