We do high performance computer vision in the browser (at 30/60 fps) that's an order of magnitude faster in WASM than JS. It simply would not be fast enough without WASM.
What types of operations are 10x faster in Wasm than in JS? Why can't the JIT compiler compile JS to the same native code as your Wasm gets compiled to?
Without more details on their exact use case, their algorithms, and their data movement patterns, you have no way of knowing this. Doing stuff on the GPU isn't automatically faster than doing it on the CPU.