Your odds are 1/32 for one of these, making them relatively common as a side effect of the hunt for more valuable cards
Additionally, it looks to be highly impactful to Pioneer, which will make up the constructed portion of the Pro Tour
Marketplaces like ChannelFireball, TCGplayer, and Face to Face Games just dont have the manufacturing capabilities to produce their own custom sleeves and they likely outsource that work to these sellers
It's a very minor bonus, and best suited for decks that want to sneak small saboteur creatures through in combat, like a Ninja deck, for example
I also predicted Yuna would help with summoning creatures, which she does on both her cards, and that Aerith's sacrifice could be respresented with a death trigger of some sort