Perhaps but if you look at most threads, they are very tech/hacker oriented and most commenters, if you read their posts or history, are software engineers here. I think that is at least 70% majority.
Yes, I would agree with you. As an aside, I always find it interesting when a somewhat niche post comes up and you realize that HN commenters also include some folks with very different careers than SWEs - e.g. Theoretical Astrophysicists, Volcanologists, or Wind Farmers.