conhex: Why did Ray don't do the obvious?

I was looking at the top match of the first championship and very surprized about move 13. Is it the deciding mistake or is it naive of me to think that?

http://www.littlegolem.net/jsp/game/game.jsp?gid=1760287&nmove=13

(sorry if that move is already discussed)

do we have a conhex board?

What would have been the obvious move? If blue plays 13.G4(right from move 12), red 14.F8(above move 7) looks promising, doesn't it?

[game;id:1760287;move:13]

In hindsight, I should have played 13.i7 (I played 15.i7, but the extra move in that corner, 14.g4 proved to be a problem for me).  Welcome back, Hjalti!