Webpack is not been extendend

I was able to expand webpack since version 6.4 with the following configuration:

const isDev = process.env.mode === 'development';
module.exports = () => {
    if (isDev) {
        return {
            devServer: {
                host: "dev_host",
                port: 8080,
                open: true
            watchOptions: {
                aggregateTimeout: 200,
                poll: 1000

Now it seems that this configuration is been ignored, even though my plugin was successfully extend the webpack main configuration.

There is something that changed? I did not went deep on this subject but before I wanted to see if there is something that I missed? …