Shorter syntax, longer lifetime. A C# using declaration disposes its resource at the end of the enclosing scope, and that scope is easy to miss when the refactor looks like a tidy-up.
Take a method that acquires input in a nested using block, calls Read(input), leaves the block, then calls Publish(). The editor offers to turn the block into a using declaration at method scope. Accept it and Publish() now runs before input is disposed. If Publish() throws, disposal happens as control leaves the method. In the original version it had already happened.
The editor recognized the pattern correctly. Whether this method should hold the resource across Publish() is another question, and the preview gives no hint of it. All it shows is braces going away and indentation shifting.
So what should it mark, so that someone accepting the change can see the scope moved?