Hiding bool field in schema, Plone 6. Bug?

Google Summer of Code
1

Am I missing something obvious here?
I have:

    directives.mode(show_title='hidden')
    show_title = schema.Bool(
        title=_("Show message type (Title)"),
        required=False,
    )

And it shows:

Skjermbilde 2025-03-11 kl. 21.04.36

The options become '<span class="option".
Other fields (than Bool) works with 'hidden'

If I change the widget, it seems to work

 directives.widget(show_title=CheckBoxFieldWidget)    
 directives.mode(show_title='hidden')