Is there any data on the performance cost of JS/WASM context switches? The way the architecture is described, it sounds as if the costs could be substantial, but the approaches described in the article basically hand them out like candy.

This would sort of defeat the point that WASM is supposed to be for the "performance critical" parts of the application only. It doesn't seem very useful if your business logic runs fast, but requires so many switching steps that all performance benefits are undone again.