The right answer is that it’s okay to say “humans have two arms.” Platonic ideals are fine. If you’re going to draw an example of a human for someone, it’s okay to draw it with two arms. It doesn’t somehow invalidate or dehumanize people with different numbers of arms. Thinking that it does is magical thinking, frankly, and has no real basis in material reality.
The right answer is that it’s okay to say “humans have two arms.” Platonic ideals are fine. If you’re going to draw an example of a human for someone, it’s okay to draw it with two arms. It doesn’t somehow invalidate or dehumanize people with different numbers of arms. Thinking that it does is magical thinking, frankly, and has no real basis in material reality.
the way this is expressed is “humans typically have two arms”.
the other statement is " humans can have 0-4 arms".
so it’s just a matter of choosing words carefully, of using precise language. you can express any of these concepts without any confusion.