From what I understand, your acf/update_field_group filter should not be necessary. All field group settings are automatically stored. ACF stores field group settings in as a serialized array in “post_content” for the “acf-field-group” post.
I would look there to see if the field is already saved before trying to do it yourself.
Notice that the documentation includes no examples of adding any filters for updating the settings. The only time this should be necessary it when the value should be stored in a different way than ACF is already storing it.
Some other notes
– As far as I can tell acf/update_field_group only happens when saving JSON
– I’m pretty sure the value of your new field will be in $_POST['acf_field_group']['is_component'] and not $_POST['is_component']`
