I don't know if that was always the intention. I don't know the original authors of systemd personally. The original announcement blog post definitely does not make any claims to be more than just an init system[1].
That said, at one point the Apache Foundation was just about a web server and the GNU project was just about a compiler.
I'm not arguing for or against systemd here, I'm just saying that the days of thinking about systemd as just an init system are over. They're building an entire framework for a Linux distro. You can agree or disagree with that, but talking about systemd today as an init system that has sprawled is obfuscating the situation. The systemd maintainers today are clearly trying to go beyond just an init system.