I feel software release announcements function as a way to "advertise" some relevant software on HN. Why should that be forbidden but Show HN be allowed?
Just to help people who never knew of it to discover it. The same like when people post links to Wikipedia articles about some curiosities every some months. OpenTTD is a masterpiece free game and can make some people happy.
Now posts about complex signaling and a station layouts? That’s interesting.
A minor point release with zero new features, only a few minor bug fixes? Not interesting.