It's fundamental in that it's harder because there's less information per token. But we know it's not impossible because they can get nesting right at all, it's

It's fundamental in that it's harder because there's less information per token. But we know it's not impossible because they can get nesting right at all, it's just a question of where the boundary is today. And if different models have different crapping-out points, then there's a gradient there and future models can do better. In token terms it's more like the fingers problem than the strawberry problem. ")" is a single token, but the model gets confused by several repeats of the same thing.