I don't know much about Pynecone, but that is indeed what pyodide does:
> These include many general-purpose packages such as regex, pyyaml, lxml and scientific Python packages including numpy, pandas, scipy, matplotlib, and scikit-learn.
Again, not super familiar, so I don't know the level of effort required to support these libraries. Maybe adding pytorch would be infeasible, maybe they just need enough people to express interest.
https://pyodide.org/en/stable/