Can it? Maybe. Should we care? Probably not. Why? Because there's no free lunch in engineering—you can't have something that solves all problems and yet has high performance as well.
Think of what would happen if the result were negative. Like, what if the size of transformer needed to represent the KF grows exponentially with the dimension of the linear system. That would certainly cast doubt on the prospect of using transformers for filtering-like problems. It might also suggest changes to the transformer architecture to fix the issue.
Since the result is positive, our belief that transformers are reasonable for filtering-like problems is strengthened a bit.