Perhaps, but on the other hand there is withUnsafeBytes(_:) on Array and withUnsafeBytes(of:_:) and the aforementioned init(unsafeUninitializedCapacity:initializingWith:) on Array, so the precedent/logic isn't that clear here.
Edit: I'm not sure withContiguousStorageIfAvailable was that great a name, really. When looking into the history here, this API was proposed and reviewed with the name withUnsafeBufferPointerIfAvailable. The name change seems to have been made at the last minute after the end of the review for reasons I couldn't find and don't appear to have been mentioned in the acceptance rationale. Strange.