Follow is not enough. In a narrow sense, social media alone is not enough. The definition should be expanded somewhat. Like, Telegram and private chat groups on Signal are more 'social' than Nostr. Weblogs can be social too. They're even the first social media. Then think about email etc.

I don't see any sense in a standard that is narrowly confined to timeline-based platforms. However, as an independent, open format, it would make much more sense and would also be ready for the next big thing.