Cannot get the score of toronto3d with the links to the respective weight file

### Checklist

- [X] I have searched for [similar issues](https://github.com/isl-org/Open3D-ML/issues).
- [X] I have tested with the [latest development wheel](http://www.open3d.org/docs/latest/getting_started.html#development-version-pip).
- [X] I have checked the [release documentation](http://www.open3d.org/docs/release/) and the [latest documentation](http://www.open3d.org/docs/latest/) (for `master` branch).

### My Question

I use the weight file linked to RandLA-Net (tf) model of the Toronto3d dataset, and use run_test() to get the miou score ,but i can only get 0.208 miou and 0.384 overall accuracy. Even if i train the model from scratch, i only can reach 0.418 miou score, anyone meet the same problem or know the reason why?