I'm just going to throw this out here in case I can't figure out how to replicate it. I would make a video of it, but I am going to wait and see if I can replicate the skip. I was doing some practice in Shore, and you can go OOB quite easily once you have gone through the last triangle and go back into Shore using seeds. I was wandering around seeing what was loaded when i ended up past Cove and into a valley area that was around where Swamp or Woodlands would be. I headed straight and found a triangle along with some other geometry that unlocked Rainforest. I've tried replicating it but can't find the valley area that I went through. If someone wants to try finding it or if I find out how to replicate it, I will update here. I don't want to get any hopes up, but I will say that if this skip doesn't lose any time or saves time it would be the best route as it skips Cove, Swamp, and Woodlands and you would chapter select into Rainforest, which should always load Caves.

I spent hours doing attempts and finally it clicked. If you use the OOB in Caves you can not only get over the wall glitch but also possibly make it faster.

Her's all the OOB I could find. The only one with any real promise is either Caves if there's a faster set-up or Swamp since I was able to test it and it unlocks Rainforest, although I'm not sure it's any faster since you have to navigate the wasteland. Rainforest wouldn't unlock Mountains with how I'm doing it so for the moment it seems to not be useful. (Sorry if the video is kind of a mess. A lot of this was me experimenting and figuring this out for the first time. While I knew how to get OOB I don't know all of the side effects or what all you can do yet.)

Found a way to clip through the door in purgatory after you pick up the notebook. I've only gotten it to save around 5 seconds, but I think if done optimally it could save around 10. (Edit: Did a test run and found that this can save up to 15 seconds.)

I was practicing some levels and tried to see about the Pacifista fight and tried out simple controls for the first time. It skips tutorials and I was able to get a method that if done efficiently enough, could save up to 15 seconds give or take. This was without doing Heavy guard breaks which would save even more time, but as far as I know it is random what simple control attack you get so I couldn't do this method reliably. If anyone wants to try and figure out simple controls, it would save a lot of time not only in this fight, but in others as well.

I was trying some arc runs of akainu, and it got me wondering how people felt about runs being done out of order. It could save a little bit of time, but I know it wouldn't be possible for people who had a new save file. I tried it on Luffy's, and I got a new time and I'm not sure how much that contributed to it. Maybe it's just me being too worried about it but I would like to see how other people felt about it.

I was doing some late night runs of flow and I had this glitch happen to me. I don't know how to replicate it, or if it would help speedrunning the game, but I hadn't seen this before so if anyone wants to look into it or has an explanation I would appreciate it.