I know. However, even without the game mechanics, no one would ever mistake a centaur for a human. The moment the GM or a player narratively describes the centaur to everyone else, they'll know that they are different. And once you note the differences, you will begin to wonder what they can and can't do.
The OP said nothing about numbers.
Except that you made a claim and I refuted it.
So you are saying that mechanical attributes i.e. +2 con for whatever race gets that....are not about numbers?
And if the answer is, "nothing at all different from anyone else", the whole setting is going to feel very off to me.
Stat bonuses are not the only racial mechanics. Plenty of mechanics are about being able to do something not otherwise possible (darkvision is the most obvious example) as opposed to adding to a die roll.
Well, the thing isn't "not different" it is "without bonus or penalty." A centaur may have to climbs stairs very differently than a 2' tall gnome, but as long as they both do so without any sort of penalty it is still just cosmetic.
Darkvision imparts a mechanical benefit...60ft is a number.
For a centaur to climb the stairs, the stairs would have to be built to their standards. They might not be able to climb stairs built for bipeds.
Trition's 'amphibious' trait states 'you can breathe air and water' no numbers whatsoever there, but still a mechanic.
