Except for PHP I don't think that's a very fitting list. C for example, is not really a concise language, not even for its time - APL is much more concise. C is rather verbose.

Likewise, Python is not the first language without braces - and it debuted before braces became the industry standard. I guess ISWIM or ABC are the first to have syntactic whitespace.

Really, you will always find an earlier example for a "killer feature", at least in an academic context - in the case of your list, usually in the 1960s, in the 1970s at the latest.