If we have a JS file that requires some style file, it’s chunkhash depends on style file and it’s correct.
But if we completely removing styles from the chunk with ExtractTextPlugin, chunkhash must not change on style changes anymore.
However, currently it changes and it means that client will redownload unchanged JS file on any style change because chunk file name containing chunkhash will change.
For extracted style file itself it’s not a problem because we can use [contenthash] there. But there is no such an option for chunk file name.