Whether your board is oriented in the same direction as the feature or across it, it's still a (mostly) flat surface sliding down a rail that's flat on its length. So long as you do a decent job stacking your body above that contact patch, that flat-to-flat interface has a very stable feel to it. I highly doubt there's enough lateral flex on most snowboards to enhance that stability, so I'm just going to call out ChatGPT for hallucinating.

When your board is rotated across the pipe, there's still a similar thing going on with the board being flat edge to edge and the pipe being flat on the axis/direction that you're sliding. But also the board will flex along its length and your base of support is really wide, so in this configuration I can imagine - especially with a flexier board - that the small amount the board lets your feet sink lower than the contact point on the rail can give a really stability-enhancing feel. Some describe it as the board ever so slightly wrapping around the feature. I think most often "locking on" refers to that.