Vetiver planted along retaining walls

Vetiver is usually used to prevent erosion when planted as hedges.
But when rock walls already exist, Vetiver can be planted to reinforce them as these illustrations suggest.
The example is from the Himalayas. The grass is planted only at the extreme edge between the stones.
Hypothetically  with such sheer walls, Vetiver could reduce the quantity of stones needed to create and support the terraces.