> Being in line with the bad original design decision is another bad design decision
I disagree. Consistently going with the "bad" choice (in this case, leaking the variable to the outer scope) is better inconsistently swinging between 2 ways of doing things. Least astonishment!
> "We've made this mistake before so for consistency we need to repeat it" is such a bad idea.
no it's not. you literally have no other choice. you cannot add scopes after the fact - it is a breaking change. you cannot have some parts of the language have scopes and others not - it's so much worse for the user. think about human languages and which ones get quoted as being the hardest to learn (those with many exceptions). you're just wrong.
"We've made this mistake before so for consistency we need to repeat it" is such a bad idea. Ideally you want a way to go back and fix things you got wrong, but, even if you can't do that (which is itself a defect and you should figure out how you can improve) you should improve as you move forward.
C++ has struggled with this, so that paper authors sometimes plead with the committee not to make their proposal needlessly worse in the name of "consistency" with existing bad features. This famously failed for std::span, which thus managed to be not only a real world footgun in a language which already has plenty of footguns but also a PR footgun - because for "consistency" the committee removed the safety from the safety feature and I believe in C++ 26 they will repair this so it's just pointless rather than actively worse...