Disable vibrancy on titlebar/toolbar area of window on Mac Catalyst?

I can't seem to get rid of the "vibrancy" effect on the titlebar/toolbar area of the window on Mac Catalyst. I have a triple Split View controller.

The primary vc style is sidebar in the split vc.. And that has the blur/visual effect and that's all well and good.

But the title bar area on the supplementary column has the blur effect too and it looks kind of terrible (the navigation bar in the supplementary view controller has all of its navigationBar appearances configured with opaque content:

  UINavigationBarAppearance *opaqueAppearance = [[UINavigationBarAppearance alloc]init];

    [opaqueAppearance configureWithOpaqueBackground];
    opaqueAppearance.backgroundEffect = nil;
    opaqueAppearance.backgroundColor = [UIColor myColor];
  //set to all appearances

But I still get the blur effect on the navigation bar, which presumably is being mapped to NSToolbar. Is it possible to disable this blur effect for the column? It really doesn't look good in my app.