This was literally the exact point I was arguing against. You are countering my point by repeating the thing I was countering...?
To use my exact example. What's a more interesting difference a deer vs. a sheep or leg+ear+liver vs. leg+nose+spleen? But the deer and sheep have so much more in common than the assemblages of body parts
The mixture, the sum of the parts, is what makes things unique; not the parts themselves.
I used this one before in a different thread. Let's say faiths are meals and tenets are ingredients. If you can use three ingredients, you cannot make interesting differences. Would you rather have salt+garlic+chicken or garlic+pepper+steak? You don't look at this and think "so many differences," instead you think "these meals both suck, why isn't there any salt on the steak, why is the chicken so bland? Why not instead compare salt+pepper+cumin+garlic+chicken to salt+pepper+coriander+garlic+steak. Now both have the essential ingredients (salt+pepper+garlic or say monasteries+communion) and room for variety. If it were up to me, there would be no arbitrary limit period - you can have as many or as few tenets as makes sense for the faith. This whole system is just there so people can customize religions and they need a limit on customization, well fine; but that's like limiting the amount of traits a person can have because the character designer cannot be unlimited for balance reasons. You don't design a concept around the exceptions, design it around the norm and make special rules for the exceptions.
Put another way, take 2 Jain faiths, both need pacifism and asceticism because those are core to Jainism, now your differences are actually only down to 1 tenet; and one sect needs nudity so no room for anything else. The only way to make 3 tenets work is to make tenets much more complex, so complex that they are effectively multiple tenets in one (e.g., the argument for Buddhist not having reincarnation is typically that dharma includes reincarnation). Wouldn't it just be easier to relax the arbitrary rule of 3 tenets. I mean why 3 anyway, what's so special about that number? Things like this just feel gamey. It's like religions in Civ games, they aren't actually different just the same thing with slightly different bonuses.