The tools that exist for fuzzing speedruns (TASers call it "botting") are fairly primitive, excluding a few game-specific ones. Because of that, there really aren't that many TASes where a distributed randomised search could make improvements which don't get immediately overshadowed within a day of human attention. Improving botting tools and increasing their adoption would be more effective IMO. (Incidentally, TASVideos.org recently banned one of the people pioneering bot development.)

Meanwhile BOINC is well-established as the platform for distributed computation. If you can figure out how to squeeze its work units into Wasm challenges, I'm sure a lot of researchers would thank you.