they don't show up on the center display, no.
That is a drawback. I have to say, the Golf is just a tiny bit too narrow--or else the MIB display is a bit too low--in that my hand obscure the MIB display. Not only must I look down at it, I must also move a bit to the side.
That's a reason to like the nav showing up in the center display, or for having a HUD like Audi does. And therefore it's a reason to use the built-in nav.
It's also one reason why I still use my Garmin instead, up on the left side of the dash right where my eyes can easily see it.
But there are also reasons not to use the built-in nav. A week or so ago I was traveling on a cold, rainy night to somewhere about 90 minutes away, on a road I had never before travelled. I had my Garmin happily telling me where to go, but for grins I pushed the Car-Net button (I am still in the trial period) and asked the Verizon dude to send an address to my car nav. And no matter what, when he pushed that address down, something different came through. I have ZERO faith in that system. I never did re-visit putting my actual desired address directly into the car's nav, though, to see what happens.
Anyway, if I can't trust the built-in nav maps or the addresses that Verizon uses to push down, and if I'm instead using either my Garmin or my phone, then just don't build nav into the car.