Those of us who build and maintain large-scale Linux infrastructures would be happy to see a highly specific, highly stable mainstream distro that had no desktop package or dependency support whatsoever, so was not beholden to architectural changes made due to desktop package requirements.
He's talking about systemd. That's the only real architectural change that affects the server installs of many desktop/server distros. I don't know why he couldn't just come out and say it, though.
As you say, Gentoo or Slackware will still let you make "thin" servers if you feel the need for that.