It replaces
Task { await someAsyncOperation() }
with
concurrent someAsyncOperation()
Changing nothing about the semantics of it. It literally saves exactly one character (4 if you count spaces, although you can just delete those). How is "meaningless sugar" anything less than factually accurate in this case?
Maybe (It's a matter of opinion, and can easily be a topic of a long discussion in and of itself), but then it's just unstructured. i.e. There's no reason to use a keyword to imply that it is structured when it is not.
The moment you take such an action, you are no longer "adopting structured concurrency", in which case there's no reason to write it any differently than you would write unstructured concurrency currently.