I think the kind of "unreliability" in question is, for example, when a process starts and unlinks itself. I doubt Emacs will ever do this. Using the proc file system is "technically" unreliable, unable to cover 100% of all potential cases, but is practically reliable, especially in this case.

On Tue, Sep 17, 2024 at 3:07 PM Eli Zaretskii <eliz@gnu.org> wrote:

> From: Ship Mints <shipmints@gmail.com>
> Date: Tue, 17 Sep 2024 14:14:54 -0400
> Cc: Spencer Baugh <sbaugh@janestreet.com>, 73318@debbugs.gnu.org, larsi@gnus.org,
> acorallo@gnu.org
>
> Google's build system, gn, used for Chromium, et.al., has support for this which can provide some inspiration
> for most of the major platforms on which Emacs runs; qv
> https://gn.googlesource.com/gn/+/refs/heads/main/src/util/exe_path.cc

Thanks. That's exactly the method that I was told was unreliable on
GNU/Linux. I don't know enough to argue with people who said that
about this particular feature.