I think that is a very post-hoc rationalization to justify the silliness that is/has been eating the JS world (emscripten and asm.js show that this sort of thing has been going on for a while), but is an entirely valid reason to indulge it for free interest and experience.
I don't think it's a reason that wasm exists, but I do think it's one of the (multiple) reasons for us to invest in making Rust -> wasm an excellent experience.
+1