Ok, Geno crew, let me start off by saying that ultimately, this means
nothing. That's my conclusion on this glitch and special thanks to
@Slender for putting the big look into what we know about this glitch while peabrains like me were out
playing World of Light.
This kind Twitter user posted back in May that he noticed a glitch with Sheik in World of Light... on his
third playthrough.
There was a problem fetching the tweet
So, it's a totally normal,
natural reaction to start to put two and two together and consider the following:
Sheik is Geno's spirit battle.
Sheik's Side B has a relatively unique function in which you can blow it up at almost any time after deploying the move, sort of like a timed hit.
Sheik is a fast and Geno is a fast.
They're using Sheik as a base for playable Geno!!!1!
Again, thanks to Slender's help,
this thread turned up showing that the glitch has been known for a bit longer than Jonny Tompkins' posting about it, and it includes the reason for the glitch: item attraction ruins the move.
If you're not aware, Sheik's side B is somewhat unique in that it does not produce a traveling explosion similar to Din's Fire, but instead produces an item that explodes on semi-command, closer to something like one of the Links' bombs. However, all of those bombs are on a timer and explode regardless, or are under the complete control of the Link that summoned the bomb, where Sheik's little bomb has to be activated, like pulling the pin out of a grenade. If at any point Sheik is hit or something affects that bomb, the move essentially fizzles, leaving a little throwable item that doesn't explode. This is the way the move worked in Smash 4, as well.
So, as you can read in that GameFAQs thread, the skill "Healing Item Attraction" will move the bomb, thus disabling it. What I find very interesting is that it will function this way no matter how far you throw the bomb, maybe it's affected immediately? Who knows. But, here's a theory for why this is happening so that we don't have to wonder if Sheik is being used as the base for any given DLC character, including Geno:
Patch 7.0 applied various buffs to Sheik, and most interestingly, "The explosion can no longer be negated" in reference to the Side B. This is illustrated well in Beefy Smash Doods' video here:
https://youtu.be/cCqn1fm2S1Y?t=110
(I am leaving this as a link so you can go to the timestamp, embeds tend to break this)
Note how when Fox interrupts the explosion, he takes about 1.6% damage from the "vortex" that the bomb creates before exploding. In the "After" footage, Fox seems to take a bit more damage from the "vortex", followed by the decent damage done by the explosion itself, which suggests that
maybe (I don't know for certain), in order to make it where the explosion could not be interrupted, the vortex or maybe the explosion itself was changed to no longer be a tangible explosion hitbox, but a healing field with a negative heal rate. Because of this, since the bomb is still very much an item, the "Healing Item Attraction" will attract the item which qualifies as a healing item, despite the fact that it does negative healing, hence why it only started happening after 7.0, and why it only happens in World of Light, assumedly unless you are using a spirit that attracts healing items.
Again, this is totally a
theory as to why it took until 7.0 to notice this behavior, and may not be the case. I have never once looked at the code of this game.
Just in case you skipped over all this complicated "text" business and would like a conclusion: this is likely a glitch with an easy explanation and there's no proof that any character is being based on Sheik.