TikTok and Vine are both "short video platforms" but there really are meaningful differences. TikTok's creation tools really are important to the culture it has developed. Making it trivial to stitch another video has led to a remixing and reframing culture that is completely novel to the platform - especially regarding audio. The ML curated feed and creator funding model also encourage different kinds of engagement and video creation than Vine. These things really really matter and people who look at a content platform as
just the content format without considering the creation tools it provides will miss critical elements.
Consider an extreme analogy - the printing press. If you just understood books as "letters in ink on parchment or whatever" and you ignored the completely new tools for creation of that content you'd be completely baffled about why the sort of things available in books changed so wildly over time.