I don't remember FreeBSD or illumos calling their syscall compatibility layer for Linux Substitute.

Nor were they called “services for Linux.”

Nor are they called now, rather Subsystem.

I don't care what names marketing departments come up with.

Actually "for Linux" came from the legal department as Linux is a trademark and it's a common practice to indicate relationship with "for X" where X is a trademark (e.g. "Y for Twitter" instead for "Twitter Y" that would suggest close relationship, from the same company).

Thanks for the clarification.

It's more like a "Windows Subsystem for Linux Applications"