By having a well-defined syntax, it allows: * Other Python implementations to correctly and confidently implement f-strings * CPython to use its regular parse

By having a well-defined syntax, it allows: * Other Python implementations to correctly and confidently implement f-strings * CPython to use its regular parser to parse f-strings rather than have a special sub-parser * Lots of edge-cases with f-string syntax to work consistently As you could have read in the discussion rather than a bad-faith comment of "they are doing this just for <bad thing>", obviously no one wants to put a lot of effort into something for it to not have any benefit at all.