It isn't that a package manager should execute code, it's that it for tasks such as "install" and "remove", that's the package manager's job, and it shouldn't e

It isn't that a package manager should execute code, it's that it for tasks such as "install" and "remove", that's the package manager's job, and it shouldn't execute code for that. You still need to build the package somehow, which pretty much entails executing code. For example, Gentoo's portage is quite capable of running code, since most packages are built from source, but that's done in a separate staging area; my understanding is that the completion of this process is a set of files that the package's build code wants to install. The package manager then installs them, from which it then also learns what to remove (what files belong to that package), and if anything would conflict.