Yeah that's probably the reason he is doing this, and its not the first one who did something like this in order to meet signature campaign rules. What I am more surprised it that no one reported these type of posts where he would quote someone and wrote only "yes" and sometimes not even that.
I'm sure it's not the first time, given that there are so many members registered who participate in campaigns and bounties (and who are lazy and/or unethical). I thought I'd seen it all, but honestly I don't recall seeing anyone else pull this particular brand of crapola before.
I hadn't noticed the user in question doing what he did because I think he posts mainly in the gambling section (correct me if I'm wrong; I'm too lazy to check), which I stay away from unless I'm doing post reviews for people.
Good eyes on this one, OP, and you did the right thing by calling attention to AndySt and his tactics.