It does explain it, plus I think it works really well with the mytharc - Sarah doesn't kill humans, and it was that birthday that brought home to John what being the leader of the resistance is going to mean.

Interestingly, I read John's "accident" as not an accident. My first thought was that he was doing it to give him an excuse to go see the therapist, and then when that wasn't what was going on, I was thinking maybe it was a half-hearted suicide attempt. I love that Cameron's the advocate for him going to see the therapist for real.

I actually didn't find Cameron and the other terminator scary so much as it was a good illustration of how the terminators aren't human - they all have the same movements. (Which is also a nice contrast to the way we often see Cameron showing flashes of humanity.) But on the creepy note, I love how they used the ominous terminator theme with Catherine Weaver.