"I know that I'm not typically a werewolf when I do change," Jake said, trying to parse it out as best he could. When he was a werewolf, Jake was far away but still there. He didn't have control but he was there and he could recognize people if he wasn't too far gone in his transformation.

"It's not easy to explain," Jake said, wincing. "It's like I'm there but I'm not the dominant personality. I'm aware and I have recognition but I'm pretty sure if this wolf wanted to do something, it would overpower whatever control I do have when I'm changed."

So, he could recognize John and since he wasn't hungry and John hadn't done anything to him, it was easy to change. If John had been someone else or had maybe tried to attack him, things would be different.