The latest version of mypy / typeshed uses a protocol for things passed to sorted / sort. As measured by mypy_primer, this was a fairly disruptive change. To correctly type some usage of sort / sorted, you need the protocol, and it's pretty hard for users to figure this out, eg: elastic/eland#283 (comment)
Adding the protocol to typing / typing_extensions would make this solution more discoverable and involve less end user protocol redefinition boilerplate when used.