You miss the point dear Boy....the teaching point was you can see obstacles with NVG's that One would not see without the benefit of Goggles.
No one flies around below obstacles at night...least ways not for long anyway.
Yes...Googles do fail....rarely but they do.
When the do One merely reverts to use of Dinosaur techniques based upon the Human Eye and either NVFR or IMC/IFR flight depending upon the external visual reference.
I have flown over lots of ground which at on an overcast night was just as dark as flying over the Oggin where there was no horizon, no ground lighting, and due to the Overcast....no celestial lighting to matter.
Our Flight Rules are based upon Weather and not whether despite there being nothing to see in the way of ground lights or celestial light....reversion to un-aided flight could easily put into a situation that would require use of Instruments to fly although while using Goggles it was quite easy to fly by visual contact with the surface.
That is one of those Carriages and Horses things as was mentioned before.
Goggles are an assist....but do come with some risks as well.