Why is a __block variable is moved to the heap BEFORE the block is copied?

I know that a __block variable will be moved to the heap from the stack if a Block accessing it was copied. But the following test code show me that the __block variable is moved to the heap before the Block's copying.

That is, the four outputs are: stack => heap => heap => heap, which is not my expected result: stack => stack => stack => heap.

Could someone straighten me out?

__block int x = 0;
int *pointerToX = &x;
//1. It's on the stack
NSLog(@"x's location is on the stack: %p", &x);
int (^block)() = ^{
    x += 1;
    return x;
};

//2. I think its stack, but it's heap
NSLog(@"x's location is on the %@: %p", (&x == pointerToX ? @"stack" : @"heap"), &x); //it's heap not stack

block();
//3. I think its stack, but it's heap
NSLog(@"x's location is on the %@: %p", (&x == pointerToX ? @"stack" : @"heap"), &x); //it's heap not stack

block = [block copy]; // The variable x will be moved to the heap
//4. I think its stack, but it's heap
NSLog(@"x's location is on the %@: %p", (&x == pointerToX ? @"stack" : @"heap"), &x); //heap