There are some tarocchi games that have different numbers of cards (they skip some of the suit numbers too), and people have divined with them.
Sometimes in tarot packs created for divination people put extra cards - a few decks seem to have more than one Lovers card, or sometimes they just tack on extra cards, or rarely, leave out some.
But for the most part, it's 4 full suits, plus 21 trumps, plus fool.
I don't see a huge difference myself if you're talking in terms of what people do with tarot or other cards or astrology or runes or i ching if you're using them for oracular purposes. Different techniques to arrive at the same result.
It may be all the pop decks that have proliferated the market over the past 20 years or so that don't have systems that causes the confusion. Cards with affirmations printed on them now count as oracles - though I'm not really sure if that's an accurate use of the word 'oracle'. And those decks do seem to have fairly random numbers of cards.
Stichomancy (opening a book at random to receive a message) and bibliomancy (same except with a sacred text) are both considered valid methods of oracular divination and have been for a long time.
If you're talking about cards, I'll read Lenormand differently to how I read tarot, but I'm generally doing either one for the same reason, and they both are fairly standardised - tarot is always going to have 22 or 78 cards with certain names (aside from minor nitpicks like wands or staves, pages or princesses, etc), Lenormand will always have the same 36 cards with certain names and symbols, and traditional sibillas will have 52, but they follow a pretty close pattern, too. Sometimes someone will go so creative it's hard to tell if it is a tarot deck, but that's pretty rare.
Interpretations may differ wildly between readers, but the decks themselves have the same basic structure, artistic liberties excepted.