The game often decides where to warp the player on entering a transition based on how far the screen is scrolled, rather than the actual pipe/vine/whatever used to transition areas. This is what leads to the minus world (entering 1-2 warp pipes without having the screen sufficiently scrolled), and is used in the usual warps run in 4-2 (by getting ahead of the screen to use a later warp pipe to a further underground area, instead of climbing the vine), and in 8-4 to turn back and enter the swimming room via the closer pipe instead of continuing ahead to the 'intended' one. The run looked optimised from a first watch. That being said, since wrong warps are only used twice, and in minor ways, I am unconvinced that this goal has a significant amount to offer beyond a normal warps run.