Vitor didn't just go for a flukey arm bar in that instance. Vitor saw something in Jones ground game that leads him to believe its the best place to score a finish against him. If Vitor thought it would be best to stand in the pocket he would have. Vitor doesn't fight for decisions. He looks to finish no matter what. Vitor and his team saw something on tape that caused him to gameplan around getting a sub.
Vitor falters away when he knows he's beat. It's the story of his career.
One of the biggest reasons Chael was so effective against Anderson in the first fight is because he was super-aggressive when almost nobody else was. That's what it'll take to beat Jones, not someone who falls on his back and prays for a sub.
There are no strong submission fighters at 205, so outside of catching Jones when he isn't prepared, you're going to be hard-pressed to beat him on the ground. Go for subs if he happens to take you to the ground, of course, but willingly putting yourself into a position where Jones tends to cream his opponents isn't a sound plan.