In process of getting a screenshot which was missing for this submission, I came across issues that warrant removal. In LM v3.00+ ROMs, the pipe will make the game crash:
And in older versions, the block "works", but breaks vertical scrolling (I was already on the bottom of the screen in this example):
Some final notes about this: you can't enter this pipe from above, and since LM v3.00+, you can setup pipes that go to the overworld/beat the level through secondary entrances without requiring custom blocks. And code-wise, these ones are badly optimized.
Tested with GPS v1.4.1 (LM v3.04 ROM), GPS v1.3.0 (LM v2.53 ROM), SNES9x v1.58, in both normal and SA-1 ROMs (block was manually converted).