I see this in the top runs of any% out of bounds and I'm wondering if it's a glitch to always get the code right or if they're just getting extremely lucky. I can't seem to find any thing about it online.

its just luck

You can have livesplit display the traincode once you set the game to poppy playtime chapter 2, it shows up in the layout settings tab.

i have tried stetting it to the game it gives me no code

Aquez, watch the video in guides on setting up the livesplit. Near the end of the video he shows how to turn the code on,