What's the big deal? It's a non-commercial, non-market, FOSS undertaking that affects the majority of users and systems. "Brand" implies a commercial, for-profit market entity. The idea of "brands" should stay within the for-profit realm, but unfortunately, young people who fell victim to brain slugs (aka corporate interns who hone their skills by "taking part in free software" in their spare time) think it's a good idea to spread this logic of for-profit companies even further, to places where it is NOT needed. It's a kind of "corporate capitalism with a human face" cr_p. And that "friendlier face to new contributors" argument is bull__it, since programmers who want to contribute to foss software are not a herd of scared animals that needs 'friendly' visual cues, and usually know what they are doing. Besides, systemd's development is centralized, and its scope is too large for a single beginner contributor, so it's ideology, like a smiley face and "Welcome!" on a fence of private property.
They didn't even ask their users about their logo, why? They decided to act like an isolated corporate entity instead, contrary to precepts of non-proprietary software. I don't think community development is even a thing nowadays, everything is semi-corporate.