wxTreeCtrl always shows selected item as focused, on GTK2 and GTK3 - gtk

Question

I'm running Kubuntu 18.04 with the Breeze theme selected for both GTK2 and GTK3. Running the 'treectrl' program from the 'examples' directory on the source distribution creates the window shown below:
The window has a wxTreeCtrl with some items and a text control showing a log. If I click on an item on the tree it's background turns blue, indicating both selection and focus on the wxTreeCtrl. If I them click on the text control the caret appears, indicating that the text control has taken the focus but the selected item on the tree remains with a blue background.
Other (pretty much all other) controls change the background colour of the selection to a different colour to indicate selection without focus.
Why doesn't wxTreeCtrl follow this and can it be reverted back to the normal behaviour?
------ Edit -------
I've build a native GTK3 app using the code :
#include <gtk/gtk.h>
enum {
COLUMN = 0,
NUM_COLS
};
GtkTreeModel *create_and_fill_model(void) {
GtkTreeStore *treestore;
GtkTreeIter toplevel, child;
treestore = gtk_tree_store_new(NUM_COLS,
G_TYPE_STRING);
gtk_tree_store_append(treestore, &toplevel, NULL);
gtk_tree_store_set(treestore, &toplevel,
COLUMN, "Scripting languages",
-1);
gtk_tree_store_append(treestore, &child, &toplevel);
gtk_tree_store_set(treestore, &child,
COLUMN, "Python",
-1);
gtk_tree_store_append(treestore, &child, &toplevel);
gtk_tree_store_set(treestore, &child,
COLUMN, "Perl",
-1);
gtk_tree_store_append(treestore, &child, &toplevel);
gtk_tree_store_set(treestore, &child,
COLUMN, "PHP",
-1);
return GTK_TREE_MODEL(treestore);
}
GtkWidget *create_view_and_model(void) {
GtkTreeViewColumn *col;
GtkCellRenderer *renderer;
GtkWidget *view;
GtkTreeModel *model;
view = gtk_tree_view_new();
col = gtk_tree_view_column_new();
gtk_tree_view_column_set_title(col, "Programming languages");
gtk_tree_view_append_column(GTK_TREE_VIEW(view), col);
renderer = gtk_cell_renderer_text_new();
gtk_tree_view_column_pack_start(col, renderer, TRUE);
gtk_tree_view_column_add_attribute(col, renderer,
"text", COLUMN);
model = create_and_fill_model();
gtk_tree_view_set_model(GTK_TREE_VIEW(view), model);
g_object_unref(model);
return view;
}
int main(int argc, char *argv[]) {
GtkWidget *window;
GtkWidget *view;
GtkTreeSelection *selection;
GtkWidget *vbox;
gtk_init(&argc, &argv);
window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
gtk_window_set_position(GTK_WINDOW(window), GTK_WIN_POS_CENTER);
gtk_window_set_title(GTK_WINDOW(window), "Tree view");
gtk_widget_set_size_request(window, 350, 300);
vbox = gtk_vbox_new(FALSE, 2);
gtk_container_add(GTK_CONTAINER(window), vbox);
view = create_view_and_model();
selection = gtk_tree_view_get_selection(GTK_TREE_VIEW(view));
gtk_box_pack_start(GTK_BOX(vbox), view, TRUE, TRUE, 1);
GtkWidget *entry = gtk_entry_new();
gtk_box_pack_start(GTK_BOX(vbox), entry, TRUE, TRUE, 1);
g_signal_connect (G_OBJECT (window), "destroy",
G_CALLBACK(gtk_main_quit), NULL);
gtk_widget_show_all(window);
gtk_main();
return 0;
}
that shows a window with a Tree View control on top and a Entry control on bottom. The behaviour is the same, as seen in the picture: