Not to harp on this idea of the girls crossing the creek by choice and BG going back across the bridge and meeting up with them on the north side of the creek, but I did measuring on a map. If the girls went pretty much straight across the creek and toward the cemetery, and BG crossed back until he could get off the bridge and headed toward the girls, he only had about 900 feet further to walk. If the girls headed towards the trail once across the creek, it would be even less for BG to catch up to them. And I think without leaves on the trees, he really probably could see them (or hear them). Walking 1000 feet would easily still fit into that "minutes" time frame LE has given. JMOMOOIMO...
If LE is truthful about the reenactments being wrong, than we're missing something. This could explain it, but it also opens others questions, like why the crime scene tape at the end of the bridge? Why not go to Abby's? Why not call somebody? IMO, I can come up with answers to those questions, but it's all guessing.
I think about what a 13 and 14 year old girl might think to do in a situation where they are scared and alone. I'd guess they would want to get to where there are people. The trail, the road (N 300 W), the person waiting for them at the trailhead. JMO