Right -- you can escape the sandbox that Lua runs in, inside Redis, and get the Redis process' user to execute arbitrary code in its environment. Redis might be inside a hardened container, or running as a privileged account on a shared machine.

redis-server is just a plain executable. Unless you're putting it in a sandbox yourself - for example, using a VM or systemd features - redis has no sandbox. There is nothing to escape from.

The Lua interpreter _within_ redis acts as a sandbox, which got a bit mangled here. Most features are not implemented in Lua, though. So this is only used for things like the EVAL command.