Both pillow and beartype work perfectly, but the warnings are still emitted, as of PyScript 2026.1.1:

As far as I understand, the warnings are emitted here:
https://github.com/pyscript/polyscript/blob/main/esm/interpreter/pyodide.js#L90
and the data defining if the warning would be emitted or not, are located here:
https://github.com/pyscript/polyscript/blob/main/esm/interpreter/pyodide_graph.js
As far as I can see, Pillow is mentioned, but emitted warning mentions pillow.
I'm not sure which lettering is correct, but the warning seems to be caused by this discrepancy.

As of beartype, it's not mentioned, but it definitely works under PyScript and is very useful.
I don't know what are the criterie for whitelisting a package, but from my point of view beartype doesn't deserve a "might not support" warning.