You are correct. GNU has the bad habit of only working with itself as well. Systemd only works with Glibc so it fits in well.
The reality is that GNU is just a subset of the Red Hat Linux platform these days. Systemd is another part. GNOME is the other big chunk. They are all designed to work with each other and do not care if they work with anything else.
“It’s more like gnu”
You are correct. GNU has the bad habit of only working with itself as well. Systemd only works with Glibc so it fits in well.
The reality is that GNU is just a subset of the Red Hat Linux platform these days. Systemd is another part. GNOME is the other big chunk. They are all designed to work with each other and do not care if they work with anything else.