Everything you mention I think is true concerning the timing. There are also the unspent cartridge evidence and the white van confession along with all this timing.
This post made me realize something about why this case is so confusing. The bench at the 505 trail where it intersects with the 501 trail at the Mears entrance faces away from the parking entrance and overlooks Deer Creek. This is a minor factual error and is not that significant.
The part that is significant is when Richard Allen says this statement about sitting on the 505 bench it probably has to be a lie. Why? Because in order for him to have murdered Abigail Williams and Liberty German after getting off platform 1 he would not have gone back to sit on the bench at the 505 at all. In my opinion, it takes too long walking (5 minutes there to bench and then 5 minutes back to Monon High Bridge). BB's testimony is that she saw Abby and Libby about halfway where she passed them on the 501 trail as they were walking towards the Monon High Bridge where it is assumed Richard Allen was still standing on platform 1.
Or there is a very remote possibility that Richard Allen, after passing Abby and Libby on the 501 trail, walked all the way back to the bench overlooking Deer Creek at the 505 trail start, and after sitting there for only a short time, minute or two, decided to walk back down the 501 trail to quickly cross the Monon High Bridge to catch up to Abby and Libby. This has to be considered since Richard Allen is not in the 2:07pm picture of Abigail Williams with the start of the Monon High Bridge in the background.
I could not understand the purpose of the 505 trail bench lie. Why not just tell the police he got off the bridge and walked back to his car and left? The timing really does lock Richard Allen into the timeline based on BB's testimony of him on platform 1. For some reason Richard Allen decided to add that little detail about sitting on the 505 bench to his story. Why?
Because that's how practiced liars lie. Partial truths garner trust.
For years, people debated the images. OBG, YBG, couldn't be the same person, had to be the same person. I think iirc even DC bridge. not to get hung up on the likeness, which should have been a clue but only makes perfect sense in hindsight.
No one claimed to see RA on bridge.
Three juveniles (plus one too young to consider) saw one person (described uniquely by three different girls but never describing three different people) who matched the man in Libby's video, BG. Same with BB and SC, they saw the figure in Libby's video. (Additionally, BB was there earlier -- her first two loops) and the juveniles were there earlier too, and none of them saw BG/RA then.)
RA confessed to being there. Dressed just like BG, his vehicle and the juveniles and BB put him there in the 1:45 pm range. He says he's the guy in the photo -- so long as it's not from the girls' camera (IMO based on his size in the released photo, BK thought they'd no way it came from the camera because HE WOULD HAVE SEEN THE PHONE. He just didn't know how LE stabilized the video and how they isolated the image.) In any case, RA could not provide any sort of alibi to get him off the bridge, and he didn't say HE saw anyone that matched the photo, didn't say HE passed a guy who looked just like him.
There's no great mystery here, unless the fact that it took 5 years to arrest RA, but even that isn't a mystery. He lied to KA, his tip to LE was buried, and no one else knew he was there that day.
The value of that video cannot be discounted.
The juveniles saw BG, BB saw BG and Abby&Libby saw BG. It creates a triangle RA can't get out of.
Why mention the bench? Maybe he did sit there, maybe he didn't. Mostly we know thst he just happens to know where it is and offered it up to account for his time and in a way that seemed credible, how ever irrelevant. He wasn't on the bench when the girls were being murdered.
IMO RA worked hard to tell a tale, had to admit he was there, in a way that made him look harmless, inconsequential. Never saw the girls. But we know he did.
He also didn't want to put himself anywhere near either of the two crime scenes nor the HH road.
We can of course argue about what time BW and his ban drove through, but the confession (only the killer would know)
isn't contained in BW's van. The significance is that RA confessed to two crime scenes! No one knew that. No one knew that RA spent 14 minutes or so DTH before moving to the second location. You don't have to believe ANYTHING about BW and his van to see that RA COULD NOT HAVE known there were two stopping points UNLESS HE WAS THERE.
(He's still not telling us what he did for those f o u r t e e n m i n u t e s. With two little girls, forced to disrobe, at gunpoint.)
And why WASN'T RA/BG in the 2:07 photo? He himself answers it. He FOLLOWED THE GIRLS. He had to exit the bridge in order to follow them, had to let them pass him in order to be behind them.
If he was still on Platform 1, they would have waited for him to complete his journey across, whether toward or away from them, and quite possibly abandon their walk-across to steer clear of creepy guy on the bridge.
He may have left Platform 1 in order to follow BB (as a potential victim? As a potential witness?), only to meet Abby & Libby as they approached the bridge.
We'll never know what he may have said but IMO he creeper them out, likely determined he was no threat because he was walking AWAY from them.
He could have said, Nice day for a swim." Creepy.
Could have said "are you girls here alone? It's not safe..."
"Can I take your picture?"
"You remind me of my daughter."
"I'll race you across."
But even saying nothing could have been plenty creepy.
Leering.
Smiling.
Refusing their greeting.
They just had no way of knowing how utterly, inescapably dangerous he was.
If only the bridge had given out under the weight of him. He was HEAVY, carrying the devil on his back.
JMO