Me with my friend, did a little research into modding, and here what we found out.
-The code is compiled with il2cpp and encrypted with obfuscator, so we cant do much, until some one will revers-engineer it.
-Henry used Magica Cloth and Houdini plugin (and some more), because of what, custom models is hard things to do.
-Primrose model is already in game files, it cut out in some pieces(Like mouth and all parts of clothing) and made into prefab.
-My guess - .TFA is packed files of model with prefab and sounds, we don't know how exactly Henry packed files, but i think he did it with Houdini. Renaming prefabs and zips will not work, there's was used some asian magic : )
Use this info to look deeper into it and, maybe, you will be the first who solved these riddles from our Taiwan friend.