The thing is what you linked to is only what happens inside the form type. But later on when the form is rendered the described guessing is happening inside the form theme: https://github.com/symfony/symfony/blob/62ecae9ab5225a0f3374e89ac276ebb3d22eb8f5/src/Symfony/Bridge/Twig/Resources/views/Form/form_div_layout.html.twig#L304-L313

Hmmm… I wasn't seeing that using the div_layout theme. I'll check I wasn't overriding anything.

@xabbuh I don't think the date time widget renders the form_label_content in the theme template at all. It skips the row rendering for the form.date and form.time children and renders the widget directly. Therefore no label is rendered. So I think this config option never gets applied.

Default theme, no css:

Theme html:

https://github.com/symfony/symfony/blob/62ecae9ab5225a0f3374e89ac276ebb3d22eb8f5/src/Symfony/Bridge/Twig/Resources/views/Form/form_div_layout.html.twig#L105-L141

If the option never gets applied, this rather looks like a bug to me. Can you create a small example application and open a bug report in the code repository for it?