Well, 'undiscovered' means nobody can find a reference to it on google. My cousin noticed this around 1989, I very clearly remember him yelling at me when I did it wrong. He didn't bother to put a dated reference to it on the internet at the time...
Haha! Yeah, I'd bet money that this has been found by dozens, if not hundreds of people independently over the years. The entire trick to winning the game (as my ridiculously-talented ex-roommate once taught me) is to watch carefully for subtle timing cues and use them to punch at the correct moment - if you do it right, you can win very consistently. So people have been scouring the pixels for these kind of cues since the game first came out!
You can even do it [without sight](https://youtu.be/CvzIb53Lcno). And yeah, TAS'ers, speedrunners and others have been analyzing these games bit by bit (literally) for years. I'd be surprised if this hadn't been found before.
Ha! Strange that this is a new find. I got more than one "easter egg" like this simply by writing a letter to Nintendo America back in the day, and asking for help. They'd usually write you back with suggestions like this.
The one time I ever called Nintendo was when I stumbled across the Chris Houlihan Room in Zelda for SNES—and they didn't know what I was talking about. I was half disappointed and half impressed to have stumped a Game Counselor. I wanted to know what the hell I had found!
I'm just going to me-too this. This was way obvious to every child in my neighborhood. Next they are going to tell us the white mushroom houses in Mario 3 are undiscovered.
