I’ve spent like eight years with Ubuntu and realize it’s all symbol manipulation to me. I learn what is and goes where but all in practice and never because I understand the semantics.
https://www.freedesktop.org/wiki/Software/systemd/TheCaseFor...
He's even added a warning to dpkg and a "usrunmess" tool to switch a system to his preferred way of doing things.
It's not clear to me where the breakage lies and I've not seen any actual reports of it.
For more context see https://lwn.net/Articles/890219/
Suppose a package has a boot-time, size-optimized, limited binary in /bin/runk and a user-optimized, feature-complete binary that requires the entire system to be up in /usr/bin/runk. When /bin and /usr/bin link to the same directory, the package manager will extract these files and run into a problem.
Things become even more complicated when these tools are split into different packages (say runk-boot and runk-user). Tracking which file comes from which package can become near impossible.
Of course this can be resolved relatively easily; make the package manager link-aware by handling the merged-bin setup as a special case and warn or error when files conflict. People don't seem to want to do that for various reasons, some good, some based in opinion only. It's a mess.