Site settings in 4.x uses the new "groups" feature, so it's not "flattening" fieldset data anymore, as it doesn't expect fieldsets to be there.
Display-wise the Collecting settings are just stuck in at the top, which isn't so bad, but more relevantly changes to the settings don't get applied.
Switching to the "groups" system instead of a fieldset is the obvious fix, but it does imply that any module doing the same has to make the same change.
Site settings in 4.x uses the new "groups" feature, so it's not "flattening" fieldset data anymore, as it doesn't expect fieldsets to be there.
Display-wise the Collecting settings are just stuck in at the top, which isn't so bad, but more relevantly changes to the settings don't get applied.
Switching to the "groups" system instead of a fieldset is the obvious fix, but it does imply that any module doing the same has to make the same change.