It's false to equate the hair vertex cache with keyframed joints just because they're both related to animation. They are fundamentally different systems.
A vertex cache animation only functions with the specific model it was created for. It cannot be ported to another model. You cannot change even a single vertex in the model, or the cache will break. But a joint animation, by contrast, is easily ported between every skeleton with the same naming convention, and it is standard practice to keep all skeletons in a pipeline built with the same hierarchy for this very reason.
If you've ever looked at modding Smash, you'll see this in action. It's very easy to attach any given model to another skeleton and have them use those animations. But many amateur modders are completely incapable of including face animations in their mods, because those are not handled by the skeletal animations, but instead by vertex shifted blend shapes. These cannot be ported from one model to the next, and have to be created entirely from scratch for the new model.
But it's a moot point, because the file that would be being reused in this scenario is not the animation. The animation is clearly labeled "Jane." It belongs to her. The file that would be being reused here would be Jack's character model, and as stated, that's just not how it works.
I think those are good points. He did add some other things yesterday too..
wilddvine is trying to find a case where they would've copied over the whole thing and used the files without renaming them. or quote:
"The developer working on this particular Jane file doesn't bother to change the Jackc06 file they're working in to simulate ponytail physics because it's still mostly Joker's file, and they're going to rename it to Jane once they're done anyways. However, the new animation is given a Jane name because it's an all-new animation that Joker doesn't have. "
So it's pretty specific and even if it's odd, there could maybe be a way for them to make the model on top of joker's and not bother changing the name of the files. I know it sounds weird, but I'm just trying to entertain the possibility.
Let's say that would somehow be something they somehow do, I suppose in that case it'd be a new model with the old animations aside from it, but I'm wondering what you think about that.
For me it doesn't make too much sense that they wouldn't rename the file even in that case. The development and modeling process is too big of a task and takes long, and especially at certain points they would make different iterations and need to share certain versions with the team, and it'd be confusing if they didn't at least add version numbers. Would they really add that to the file without changing the 'jack' part of the name? That'd be super weird.
And we can see from the file they found itself that there are version numbers and more numbers probably for other distinctions, so I'd find it hard to think that they wouldn't do the same for other character projects they're working on. That's my thought on it right now anyway.