Postcss plugins in Angular/cli v11.2

I need to postcss my css with plugin postcss-preset-env for IE11 compatibility (don't ask). I saw solved issue https://github.com/angular/angular-cli/issues/8427 which indicates that tailwind conf is now supported by adding tailwind.config.js in project. But it does not tell anything about postcss explicitly.
I saw an example here https://gitlab.com/-/snippets/2095311 where postcss.config.js is added. I tried it with this postcss.config.js

module.exports = {
    plugins: {
      "postcss-preset-env": {},
      autoprefixer: {},
    },
  };
  

And it works, my css is made IE11 compatible. The same file added in angular/cli 10 has no effect.

I see no indication of that in docs or release notes. In fact it's the opposite, on the official tailwindcss issue, it's said that postcss config cannot be exposed : https://github.com/angular/angular-cli/issues/8427#issuecomment-773557085

So i'm confused, is the support of postcss.config.js official? Or a side effect that should not be used ?

Thank you