Comment 3 for bug 1510540

As far as I understand this is not a problem with themes but it depends on the app whether it actually enforces the both-horiz setting (i.e. showing the text next to the icon in toolbars).

If it's not explicitely enabled on a GtkToolItem, this setting does exactly nothing:
https://developer.gnome.org/gtk2/stable/GtkToolItem.html#gtk-tool-item-set-is-important

So I would presume that everything is fine and that this is not a bug.