I do know it's a niche use case. And I for sure wouldn't recommend that every man and his dog use the polyfill. I'm not even sure it's right for the scenario I'm thinking of. But I can definitely contrive a case where it is.
I haven't benchmarked this specific thing, because I've never used it. But I might, because it sounds like a fun thing to do.
I sometimes render 50mb PNGs. The execution of decoder is insignificant compared to everything else.
Also, my go-kart also gets more miles to the gallon than NASCAR team cars.