I only mentioned Fx keys in passing - my point was that they key was not present in the context menu which is a very common idiom to indicate action is not bound to any key. If all actions have key and this one doesn't: the first natural though is, well, this action has no key. The fact that it's leftout and hundreds of other similar anectodes really shows off that macos is not any more magically intuative than any other OS and has lots of space to grow.
But I would argue F2 is less obvious. It's only obvious if you learned it at some point or if you were there when F2 was chosen. Enter is at least a normal text editing key for day to day typing, and it's already the bookend key to finish typing a new name.