I like that it forces you to explicitly think about what a script actually needs (files, network, etc.). Most shell scripts run with way more access than they should.
Feels like a good middle ground between “no isolation” and heavier tools like bubblewrap or firejail.
That first example, it's a no-op for a regular users, they can't write those, use chmod/chown instead.
What you don't see is that this sort of thing, permissions within the scripts, are (1) easy to change (2) hard to maintain