When looking inside a part or MeshPart/Union with collison fidelity set to Box/Hull, collision detection isn’t drawn inside, which is normal.
However, if the collision fidelity is set to Default or PreciseConvexDecomposition, unnecessary collison data is drawn inside the object
The physics engine works a bit differently than rendering. Rendering cares about triangles, as the smallest form of objects, while physics deals with primitive and convex shapes as the smallest form of objects. Both Default and PreciseConvexDecomposition will approximate the mesh using these small convex objects, and this is expected, as it is more efficient to run physics calculations on these convex objects than it is on individual faces.