Here is the surface produced by Freesurfer:
Note that this very smooth cerebellum surface is not produced by FreeSurfer, it is meshed from the ASEG volume parcellation by Brainstorm using Matlab function isosurface.m, called in function in_tess_mrimask.m.
https://neuroimage.usc.edu/brainstorm/Tutorials/LabelFreeSurfer#Subcortical_structures:_aseg_atlas