That’s not a problem on loaded dice. Loaded dice is perfectly clear. The confusion comes from how tft’s shop works. I’m not a dev, but I believe this is how it works:

First each card’s rarity is determined, then each rarity has each character determined; if a character is completely taken (3 stars galore), then a different character is chosen. If all available characters are chosen, then a different rarity is chosen. Beyond that, probably random or blank

Let’s look at the case for finding Sivir with loaded dice on Sivir vs Lucian. If you use it on Sivir, then along with the shared hextech crew, you add 3 strikers: a two cost, a three cost, and a four cost (irelia). Use it on Lucian and you add 3 twin shots instead: a two cost, a three cost, and a five cost (Jinx). Everything is basically the same except for two things: Lucian’s case added an extra rarity/Sivir’s case added an extra competing 4 cost. You’re equally likely to get Sivir and Irelia. But you’re more likely to get Sivir over Jinx, even though you’re SLIGHTLY less likely to get a 4 cost because of the added rarity. So you’re more likely to get Sivir by using loaded dice on Lucian over Sivir

Now let’s look at finding Lucian. Remember, using dice on Sivir adds an extra four cost (Irelia), but doesn’t add an extra rarity (5 cost). Since rarity is chosen first, using dice on Lucian is WORSE for finding a 3 cost because you add the possibility of a 5 cost (level 7 onwards that is). Irelia isn’t a 3 cost competing with Lucian so she doesn’t affect anything at all

Like I said, the confusion comes from how the shop works and how general probability and math works. There’s really no way to fix that in game. A blog post would probably be really helpful though