HN is social media and I think most people recognize that.
It's just that HN is a social media that respects your time and doesn't try to get you addicted. For example, HN has a very useful 'noprocrast' feature and one of the co-founders, pg, has openly worried about HN's addictiveness in the past [0].
So while HN is social media, I feel like it's qualitatively different than other platforms.