Ha, interesting! I didn't realize that infinite lives in Mario games was such a thing! I remember when I was much younger (Probably around 7 or 8 years old) I used to play Super Mario 3 on the NES quite a lot. I remember figuring out this trick for infinite lives and thinking I was sooooooo clever, haha. I don't remember exactly how I found it, I was probably just screwing around with the goombas and noticed I could get lives from them and then took it to the next level.
I noticed the linked video doesn't have this trick in it, but that could be because it takes a lot more work compared to most of the ones in the linked video in which they mostly seem to be "set and forget" type infinite level glitches. It is nice how it's basically right at the very start of the game, though.