With the main model having no arms and legs and them being static meshes, my theory is that the game curves those meshes based on where the "bend" bones are located. (why they're given "spline" in the original filenames)

Models and Textures ripped with UModel

Asset: Monty
Game: First Steps
Console: Meta Quest
To be hosted on: The Models Resource

Ripped by Somwonere, credit not needed but appreciated.