If You're Not Paying For The Product, You Are The Product

The wall is on the side of the paper, not the advertisers. The whole purpose is to not pressure the news side to not run stories which will cause advertisers to pull their ads, not to try to keep advertisers from doing so. That’s a given. And nothing about the wall keeps the layout people from trying to prevent the kind of blunder you mentioned.
The advertisers come back once the storm is over. Every so often Broadway producers threaten to pull ads in the Times due to bad reviews or bad coverage - it never lasts very long.

That’s a fair description. Yes it is a wall to prevent influence from advertisers, but they know the game, they’re better off pulling their ads for a while instead of trying to cover something up.