Need some urgent advice.

We’re currently having our garden wall redone with stucco/plaster. Wall guy has left a really large gap at the bottom of the back wall, according to what he sees as a grading issue that will correct itself when we regrade.

We’re regrading the yard soon, and having gravel surrounding the edges near the wall, but i don't want to be raising the yard up to fill in this gap. He’s not a landscaper. i actually wanted to take the wall really low down and we would even things out ourselves with the grading. I don’t want him guessing at the grading.

Does this sound fair? We don’t want him coming back to patch up later.