See its absolutely an understanding thing but its understanding that "split" means "split from this topic" or "remove from this topic" it doesn't mean "merge into another" or "move into another" I think, overall, "move to another topic" being the default is actually more confusing then "split from this topic" overall.
Not everyone will understand the specifics depending on the community, you're both correct, but if you leave people uneducated then it can be overall more confusing because you're NOT moving a post. You ARE separating a post from its parent topic (the one that the person replied to) though which is "splitting" the topic. This has been the terminology for it since 3 so with this software for over 10 years.
I will concede that "split" often means that anything after X is being put elsewhere but that's just.... splitting hairs?
Could there be a better term? Possibly. I don't think move, is it. Because honestly what you all are thinking is move isn't the same to me. When I use split I intentionally want to separate the posts I choose and place them into a completely new conversation therefore "split" the conversation. I'm not "moving" the conversation. I'm taking the conversation that has derailed and split it to a new conversation that requires a different point of view which is the point of "Split" if you use it for other purposes or in other ways how is that the responsibility of IPS?