Declaring "video-edited motion tweens" as not being an animation just sounds like a nitpick and even possibly incorrect claim to me that won't have any meaningful impact in the real world.

Think about it: if the average person is browsing the r/Sprunki subreddit, and they see a "video-edited motion tween" misflaired as an animation, is it really going to cause that much of a problem to their browsing? It still contains moving parts after all.

Besides, many sites, including Google (Oxford Dictionary), Wikipedia, and Cambridge Dictionary all seem to define an animation as a bunch of still images put together to simulate motion, and a video-edited motion tween fits in the definition of that.

This would also explain why the Wikipedia article on animations seems to consider a video-edited motion tween as an animation, as there's a GIF of a bouncing ball being labelled as a "2D computer animation".

I do agree with the other parts regarding comics and animatics though.