The champion you play has no correlation to the results you see from the crate, the only stipulation there is for champions will be you have to own the character you play in order to be rewarded.
There are 2 sections regarding champions, a chance to earn champions you don't own yet and a chance to earn skins for champions.
Even if you don't own a champion you have odds of getting skins for it, you won't have access to the skin until you buy that champion which seems odd why give skins for character you don't own.
there's a detailed link here which could answer more questions you have about hextech.
http://leagueoflegends.wikia.com/wiki/Hextech_Crafting
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