Isn't it just the ABI and basic semantics that is never supposed to be broken? By extending that logic one could say that the kernel should never patch kernel exploits since it'd break things the exploits expects, naturally this is a silly hyperbole and i do understand that the line has to be drawn somewhere but chroot is old and imho additions that has enabled breaking out would have broken the original semantic.

I do see the usage for bootstrapping and troubleshooting so that does cause an issue.