The security researchers will leverage every part of the OS stack to bypass the sandbox in XNU which they have done multiple times.
Now, there is a good reason for them to break the sandbox thanks to the hype of 'agents'. It could even take a single file to break it. [0]
> My guess is sandbox-exec is deprecated more because it never was adequately documented rather than because it’s flawed in some way.
You do not know that. I am saying that it has been bypassed before and having it being used all over the OS doesn't mean anything. It actually makes it worse.
[0] https://the-sequence.com/crashone-cve-2025-24277-macos-sandb...
I hear what you're saying about the deprecation status, but as I and others mentioned, the fact that the underlying functionality is heavily used throughout the OS by non deprecated features puts it on more solid footing than a technology that's an island unto itself.