A few releases back they replaced the python parser with a more capable PEG parser. At the time nothing really changed, but it was done to enable this kind of i

A few releases back they replaced the python parser with a more capable PEG parser. At the time nothing really changed, but it was done to enable this kind of improvement and make it practical to evolve the syntax over time. This change isn't so much done for the sake of being able to next quotes in f-strings, it's done because there was a dedicated extra parser for the python syntax inside f-strings, but with the new parser this can be parsed without this special case extra parser. It's all to manage technical debt.