You missed my point though but brought up a better way to put this. Finding exploits in an RPG system is not a cheat, even if the exploit was unintended, it';s still the player learning to work the system for them. The Invincibility Leaf on the other hand is not a good design idea, it's basically a built in cheat for people who can't be bothered to put the time in to master the skills the game asks of it. Even worse, it can quickly become a crutch item as the item will always help the player complete the stages with ease, but each use basically denies the player the chance to actually master the skills needed to finish certain obstacles, meaning they'll have to resort to it when it comes again or harder obstacles present themselves.
It's like seeing a child in elementary suffer in a subject they don't like, yeah the teacher can give them a pass, and that may boost their confidence temporarily but it will hurt them in the long run as they never mastered the fundamentals of the subject. Likewise, I feel the item just hurts the players ability to get good at the game or learn to appreciate it.
I'd rather have an easy mode that may deny the player some things to spurn them on to try a higher difficulty and become better; than an item that just let's you win because a person can't learn the patience to put in the time to be better at something they say they love. I'm not against easy modes, but I don't like easy games.
To be fair, many of the cheats and codes of games from the old days were never intended to be used. They existed in the code as shortcuts for the designers and play testers to skip around and check quality control. They caught on, and many games in the future added them in since the kids who grew up playing those games and exploiting the codes thought it was fun, but I feel there is a strong difference between mods that balance and add a few fun things to games as opposed to adding an ability that just lets the player win. I don't imagine Skyrim would be a fun to play if you could enter god mode where all your attacks are one-hit-kills, you can't lose health and you succeed at every attempt at theft and persuasion with no risk of screwing up. Might be fun the first time you try it to dick around, but I doubt most players would ever finish the game like that.
Mods in my mind is a different beast, if you want to play a mod that adds in an easy mode that's fine and can be great for people who only want to enjoy the story of the game, but I feel that cheats that rob the player from learning the game mechanics or acquiring the skills needed to be a better player hurt you more in the long run.