It's a social experiment because Rocket himself has stated time and time again, that this is more of an emotional social experiment over actually being a zombie survival simulator. He has stated time and time again, that zombies are a third party, and that the human emotion/reaction play is the main feast of the game.
This is why when people cry about the game being too pvp centric, they are just feeding him delicious tears.
The thing is though... I mean the thing with that... Well the problem is that Rocket is kinda full of shit.
If it's such a social experiment about delicious tears, then when people realised the Arma2 engine has absolutely no protection to stop people from running any script they can think of, including spawning nukes on top of every player in the server, Rocket should've been over the moon about that! Instead he spat his dummy out and threw a tantrum. (Proving that his tears are the most delicious of all I guess?)
I mean Rocket also says it's "not a game" and yet it has a headshot score counter. Rocket just says things. The term "social experiment" implies some sort of hypothesis or goal. If giving people an envorment to interact in is a social experiment then everything and everyplace is a social experiment and the term is meaningless.
I mean Rocket removed the starting weapon and ammo because he wanted to limit early-game PVP. So obviously even he thinks it was too PVP centric? But then he keeps saying things to the contrary.
At this point the term "social experiement" has been so bastardized by the gaming press that it's just a buzzword.