No here is why.
1. Lots of pillars. There is Many many pillars in thousand needles, these act to break up any waves. Stopping any high levels of erosion, also they are still there and the map is underwater but the zone is unaffected, and again we know why this happened same happened to ungoro.
2. The amount is insane. It has to go through two mountain ranged and then through half of mulgore as the bottom half is far above sea level.
3. That is not how it works. Large mountains like that do erode, but it takes hundreds of thousands of years... Not 7 or 8. Now stuff like running water. And large waves can make erosion happen faster.
But the water is stagnant, and the waves would be broken by all the pillars so no. It is not happening.
4. The map in questionn is the barrens warfront. Now mulgore is copied over in the wide clip, but is not visible, so well it makes no sense. The same thing that happened with silithus and how ungoro is not visible, and so it is fine that is became filled to the brim with water.