Yes, and macOS entitlements work similarly, as you know. I was interpreting “what it expects its children should be able to do” as a single rule for all child processes, like in OpenBSD pledge() which the parent seems to be referring to. Sure, such a rule could securely be greater than the parent’s own permissions if you strictly limit what processes can be executed with what arguments.

Actually, there’s another exception to my previous statement that I should have mentioned. For mitigations that are meant to prevent an attacker from turning memory corruption into code execution or code-execution-like control – such as restrictions on mapping memory executable (at least that’s one purpose for such restrictions), or memory map lockdown – the mitigations’ effectiveness doesn’t depend on whether they’re applied to children. Those mitigations are sometimes treated as part of the sandbox system, sometimes separate.