I don’t think the any interaction definition is too broad at all. Primitive forms of social media such as mailing lists and forum threads form are very similar in functionality to simply following hashtags, or I guess whatever the algorithms suggest.
The distinction using account based versus conversation/thread based is not too helpful, because the majority of users of modern social media don’t really use it to follow accounts, with the majority of their time is spent doomscrolling generic hashtags or algorithm recommendations.
The similarities are easier to see if you think of how people actually used these technologies in their daily lives. Pre Facebook, people would log in and refresh their Usenet, emails, and forums threads to keep in touch with friends and interests. Post Facebook, people would log in and refresh Facebook/Insta instead.
Someone (allegedly) fucked the principal’s dog