This is only surprising because of the ambiguity of value types in certain cases in Swift. If you passed it to a function and mutated it then it would work as your example. I'm still not sure why they made it work this way for closures. Using reference types closures and blocks are more or less the same.
What ambiguity are you referring to? It has nothing to do with value versus reference types. Reference types have the exact same difference between the two languages. In Swift, mutable variables are captured by reference by default, and in Objective-C they're copied by default. Value versus reference doesn't make a difference. For example:
In Objective-C, this will log an NSButton. Translate it to Swift and it will log an NSTextField.
I don't think either behavior is more correct, it's just a fairly arbitrary choice. IMO it's surprising only if you've learned to expect one way because you worked in a language that does it that way, then encounter a language that does it the other way.
