Well,acording to what I have read,this was a Jake's spontaneous action,that Ang wanted to leave in the final shoot to show better how troubled Jack was before a half naked Ennis.So...
Yes, this is correct. The can opener slip and splatter of the beans was not scripted. I always love watching both these guys react to this action, Heath is particularly cool in response and his look towards Jack. He's looking at Jack just as Ennis would, with a sort of
"you dumb f**k" expression on his face. And then Jake's slamming the can down on the grill is pretty precious too. Since this scene was pre-FNIT, the guys really were able to show how close and intimate Jack and Ennis had become. But I've also thought that Ennis's remark regarding the size of the coyotes BALLS is whut flustered and distracted Jack from his mundane task and resulted in the slip, huh?