Alexander, thanks a lot for contributing this feature and the docs too! Your PR was perfect, but we removed the .. versionadded:: 5.2 directives added in components/form.rst and forms.rst because we considered that they are not needed now that this parameter is documented everywhere in the constraints. Thanks!

The documentation is confusing because it is working just inside Symfony form, otherwise label is not replaced. There are no mentions about that. I spent several hours to find why it is not working on my setup (using validation component outside of symfony form)