50KB Gzipped seems like it's just the wrapped JS code, not the .wasm code.
I'm not saying you are wrong, but if the NPM package needed more stuff it would be in the package.json, no?
If you just do an npm install of canvaskit-wasm you'll find a 6.4M canvaskit.wasm file. That'd have to be some insane gzip magic to bring that down to 50Kb.
If I gzip the entire canvaskit module (including the font files) I'm getting a size of 3.4M. If I just gzip the .wasm file I get a size of 2.4M.