That requires an ISA emulation layer, this new implementation doesn't - here, every binary is compiled as wasm, and every child process runs as a new Wasm WebWorker, and the Kernel ABI is exposed as Wasm export functions.

Removing the ISA translation layer has the potential to be massively faster for full-system environments. At the expense of maybe some new bugs.

The performance should ultimately be similar to compiling your userspace application directly as Wasm, but you now get to take advantage of the full kernel ABI instead of just the minimal shims that Emscripten give you / whatever DOM glue you create yourself.