The hook_entity_form_display_alter() allows to alter a form display after it has been loaded, and before it is applied.
The field_group_info_groups() does not respect these changes, and instead loads a fresh unaltered form display instance from config.
Configure a form display with field groups.
Implement hook_entity_form_display_alter() to change the type or label of one of the field groups in third party settings.
Visit the form.
Expected: Alterations are applied.
Actual: Alterations are not applied.
Instead of loading a fresh form display object, pass the original object via $context['display'].
Active
3.0
Miscellaneous
I wanted to give this a try, but I give up.
There are too many places that call field_group_info_groups() which do not have the altered $display object available.
Sad!
It also makes me think that in core itself this hook is not very useful.