Well I don't know...
Atkins shows him slowly approaching the curb and that's all, then there's this;
Mr. HAYGOOD. When I first got to the location there, I was still on Houston Street, and in the process of making a left turn onto Elm Street I could see all these people laying on the ground there on Elm. Some of them were pointing back up to the railroad yard, and a couple of people were headed back up that way, and I immediately tried to jump the north curb there in the 400 block, which was too high for me to get over.
Doesn't tell us he actually fell on his derriere in the process with the bike on top of him, or that it took him at least 20secs to recover from his great escape act. So he left out some details and if you were consistant that would mean these details didn't actually happen.
Also, the part I underlined has no evidence to support it, so I don't actually believe it.
So at least you have admitted now there's enough flimsy evidence for you to accept a motorcycle officer tried to pull off a ridiculously risky manouver where he attempted to ride up a grassy incline much like Steve McQueen's stunt double would in The Great Escape, probably only months after the film's release. Interesting.