embee
Lawyer by day. Rules lawyer by night.
It depends.For the record, I enjoy discussions regarding the scale of common objects and spaces in D&D settings. I think it's something I've seen a lot of DMs fail to address, and it's something that absolutely would be reflected in a place with various sizes of sentient folk running around.
That said, this particular adjudication reads like trolling. Like are you forcing athletics checks for halflings to ascend barstools? (Or dex checks for humans to avoid tripping over halfling-appropriate barstools)
If it's a goliath bar, absolutely. Goliaths are large and halflings are small. It's no different than having the halfling wield a standard two-handed greatsword with disadvantage. (PHB 147).
So yes, for something like that, give me a DC 12 to get onto a stool as a small creature when it was designed for a large creature. If you have Athletics or acrobatics, you can add that.