Not once is my decades of DL fandom have I ever thought "you know what makes Krynn unique and interesting? The fact that there aren't any orcs."
I think I'd kind of worry about anyone who thought that was the the only thing that made the world unique

W&H sure didn't claim it should feel unique solely because there weren't orcs, and they said right after bringing up orcs that Draconians filled the role as being what they had as the main non-human enemy.
It doesn't make it somewhat unique at all, because there are many fantasy worlds which have no orcs.
Sure, there are a bunch without orcs. And so their leaving them out feels to me like it shouldn't require much justification. I wonder if most of the other fantasy world creators thought about it similarly, that "
World creation isn’t like a blender. You can’t just toss in tropes, hit pulse a few times, pour out something and claim ‘it’s unique’. Worlds have to be organic, as my wife likes to say. All the parts make up a living, breathing whole." In any case, not being a kitchen sink campaign feels to me like it helps with feeling unique.
What makes it unique are the things that actually make it unique. Defining something based on what it isn't is a terrible idea.
As a total aside, lots of things are defined by what they lack though, right? Vegetarian (no meat), vegan (no animal products except probably accidental insect parts), non-binary, non-metric scaling, non-Abelian rings, non-sectarian, NGO, etc...