I don't think "you can implement this slightly modified version of the proposal in GCC macros" is a good reason to change the defer proposal. It doesn't work in clang¹ or any other non-GCC C implementation, a trailing semicolon after the close brace is an ugly wart, and saying "if you want to implement this all you have to do is implement [[gnu::cleanup]] and nested local functions" is presumably much more work for other C implementations than just implementing defer is. I also question whether this even works in GCC with executable stacks disabled (I know GCC can optimize away the trampoline since the function doesn't escape the local scope, but does GCC let you write nested functions at all without executable stacks?).

¹The author says it works in clang using Apple's Blocks feature, but Blocks should not be required for defer and the variable semantics are wrong so it's a non-starter.