I've been hung up on these details, too.The thing is, if he intended to go for a run, wouldn't he have headed down the driveway to the road, not into the backyard?
And if he was wearing only light (running) clothes, and actually left the property from the backyard, he would have had to push his way through the briars that were previously mentioned as being fairly intense.
So it seems to me he either did that, probably scratching himself up in the process, or he doubled back to leave the property from the front without being seen on any cameras, or... he never left the back yard at all.
Problem is, none of these seem overly likely. This is a puzzler for sure.
MOO
Also, if he were going for a run to cool off or whatever, he wouldn't care whether he appeared on any security cameras. It seems more likely he would have gone down the front drive. Was that the route he usually took when going for a training run?
He's also not wearing a reflective vest, which, I assume he would normally do when running after dark.