I think I discovered a bug. This returns False (i.e., indicating the property is not read only):
ExtAPI.DataModel.Project.Model.Mesh.PropertyByAPIName("MinimumEdgeLength").ReadOnly
In contrast, this returns False (i.e., indicating the property is read only).
ExtAPI.DataModel.Project.Model.Mesh.IsPropertyEditable("MinimumEdgeLength")
However, it also returns this recommendation/warning:
Method : IsPropertyEditable
Use PropertyByAPIName(name).ReadOnly instead.
Looking at the UI, it appears to follow the PropertyByAPIName(name).ReadOnly result:

Even though it looks like an editable field, clicking on it does not allow the user to edit it.