Originally posted by Super Maks 64
I think all special autoscrolls move back to screen 00 when they're activated at a later screen (which can be seen in morsel's VLDC8 level Municipal Swimming) and I suppose that the level used the Yoshi wing level autoscroll that goes all the way to the top of the level first before acting like usual.
Very late reply, but Yes.
In SMW, special autoscroll start on screen 0 and do their predetermined path.
If you start the autoscroll later in the level, it will scroll slowly to screen 0 backward. Prior to lunar magic version 3 that means scrolling to the left. But now with extended level size, it will scroll left, and after that will scroll up until it reach its starting position on screen 0 at the top left of the level.
Also it doesn't scroll straight up, it very slightly scroll right too when going up.
And to answer what you said in the video: no, autoscroll cannot override or stack with another autoscroll (in vanilla, some custom autoscroll sprite can get overridden). There is an autoscroll going right at the entrance of the level, and the special autoscroll at the midpoint entrance, and they don't get overridden by each other and they don't stack.
Irrc if you put two autoscrolls on the same screen, only one will activate.
Also, in the underground part, there is a weird autoscroll command placed at the bottom left that makes the game locked vertically to the left of the level. That's why when you go up to the entrance, you cannot go right and do the level wihout autoscroll, and why the autoscroll that goes right at the start doesn't get triggered since there's already an autoscroll active.