On the 3DS's version of SMB2j, going 'down' through this pipe warps you ahead a short way through 8-1. On the FDS ROM that checksums with the published movie, it instead warps you back to the start of the level.
I apologize for the quality (or lack thereof) of this video - I wanted to remove the needless pausing at the end, but I can't read the hex output to save my life. I am sorry. (Feel free to remove it on your end.)
Game is paused right beside the second vertical pipe of 8-1.