Agreed. However, I do think it's fair to assume that "Guys" happened at a different time from "down the hill." He's using an objectively different tone in his voice from one to the other. I think it's also fair to assume that the police released "Guys" because they realized that he spoke so differently in "Down the hill" that the people who frequently interact with BG may not recognize his voice. I do think they deliberately released a portion in which he sounded different. Otherwise, why would they release it two years later? I think they have learned from the tips they were receiving that the public perception did not match the evidence. That would also explain the change in age range. "Down the hill" sounds like an order to me. "Guys" sounds like an introduction.
Now, I could make additional assumptions, as I have before, that "Guys" occurred earlier because he sounds less commanding and at the beginning of the conversation it would be not be advantageous to show his true colors, but yes, that would be guessing. Maybe I've read "The Gift of Fear" too many times, but I believe that most predators who are not trying to immediately rob you and who approach you in broad daylight will initially attempt to be friendly or at least less threatening. Basically, accelerated grooming to lower your guard until he is completely in control.
BBM.
I cannot tell you how much I agree with this. I believe as BG started toward the girls across the bridge, they noticed him. He saw the girls notice him, so what do you do to help a person think you're harmless? You greet them. "Hey, guys." BG may have said something else like, "What are you doing?" The girls replied, "taking pictures." All the time it took for a short convo to take place, BG has gotten closer to the girls without alerting their fear instinct enough to run. It is exactly what
cfreya23 said it is:
accelerated grooming.
There is definitely a cut/splice between "Hey, guys" and "Down the hill" spoken by BG. There was more conversation between the greeting and the command that has been intentionally left out by LE, and they have their reasons.
BG may have intended his walk to look like ambling across the bridge, as if he wasn't making a straight attempt to overtake the girls too quickly. That would have alerted their fear instincts. Instead, BG walks slowly towards them. When he sees they have seen them, he acknowledges their presence, makes small-talk as he gets closer. He probably acted as if he was going to pass by them. Then, in the same instance, BG pulled out a weapon, grabbed one of the girls and held the weapon to her head or neck. This got the compliance of both girls, and he ordered them, "Down the hill."
IMHO, BG is wearing a brown fanny pack or some kind of carrier (backpack) under his jacket. There is a definite
weight shadow from it in the video that is not just a brown shirt. He probably had a pistol in there, and possibly a length of rope. Perhaps, as some have suggested, he had one girl tie the other one up under threat from the weapon. Otherwise, it is difficult to imagine how BG could overpower two young, athletic girls at the same time.
In the video, BG is wearing baggy clothing; a baggy jacket and baggy pants. The initial sketch made him look heavier than LE must believe he really is, and the clothing contributed to the public's belief that BG was an older, heavier man. It is obvious the new sketch of the younger, thinner man is more realistic to the investigation now. That means the bulk under BG's jacket was not paunch but the intentional hiding of weapons. BG was hunting prey that day. And he was careful not to scare off his quarry until he could get close enough to capture them.
I have no doubt it’s disturbing and heartbreaking, so to preserve everyone’s wellbeing, it’s in our best interest to use what the police give us. 
