Could be either, so SSK is Captain Ark or Unchained Snake.
The only plot hole that I can see in the event is that Vapaus blood type would be known the researchers in MMR if they experimented with SSK, meaning that at least one of them would have tried to take him to make a Vapaus factory out of him out of curiosity on what Vapaus does... Unless Jien had the data removed and killed anyone that tried that in order to see how far Project A.D would go.
