they want to ensure the language is never in a position where it's so important that certain behaviors or code be kept exactly the same because there's too much

they want to ensure the language is never in a position where it's so important that certain behaviors or code be kept exactly the same because there's too much code that depends on it in the wild that they can't experiment with some new interesting feature in the next release. Squeak Smalltalk had this. "Burn the diskpacks!"