They did.

It’s up to OS developers to implement it or not on their OSes

I use libsfapfs on Linux, but as always when Apple does anything open source, the Linux community hates it

Darwin WebKit Swift and its compiler APFS ALAC …

The only widely used open source project from Apple that I know is CUPS

The only things in macOS that are not open source are related to its GUI.

But you know… Apple bad as usual

As a developer, most of Linux users I know develop in Java and dual-boot on Windows to play games.