X3D_XS and X3D_S delivers the same model

Hi everyone,

i would like to use the pretrained X3D_XS variant but when i follow the instructions to download it, always the X3D_S variant is being downloaded.
I followed this guide where i just changed the line to download the XS variant, the download works, but it delivers the wrong model.

https://pytorch.org/hub/facebookresearch_pytorchvideo_x3d/

same is true for this overview
https://github.com/facebookresearch/pytorchvideo/blob/main/docs/source/model_zoo.md

Thank you for your help.

Start with the PyTorchVideo X3D guide and docs/source/model_zoo.md, then reproduce the X3D_XS download instruction and compare the resulting model with X3D_S. Done means the documented XS download retrieves the X3D_XS variant rather than X3D_S, with the relevant documentation or download reference corrected.

Written by the indexing model from the issue text.