Thank you for all the testing and replies both @laurent_delrieu and @diff-arch!
Rhino mesh vertex coordinates are defined by single precision floating point numbers:
https://developer.rhino3d.com/api/RhinoCommon/html/T_Rhino_Geometry_Point3f.htm
A rule of thumb is that for single floating point numbers, there are approximatelly 7 digits precision.
Plenty of webpages online can be found, showing how to precisely calculate it for a specific number (range):
For a given 85395.52 document units, precision is 0.0078125.
This is smaller than my tolerance: 0.01, so there is no problem with the model being far from Rhino’s origin.
By the way, we should be checking the X,Y,Z coordinates of the vertices not its distance from the Rhino origin (which is what 85395.52 is in this case) - mesh area centroid coordinates are: 24344, 81678.9, 5321.25).
Mesh should be a mesh, regardless if it is closed or not.