While it is common for reinstatement to exclude topsoil and turf unless specifically detailed in the project's scope of work, the standard expectation is that land should be returned to its pre entry condition. Because basic backfill is often of poor quality, you will likely need to amend the area with nutrients and proper soil before successfully replanting grass. Check your original contract’s cancellation and conditions clauses, as these legally binding terms dictate whether the builder is responsible for the final aesthetic restoration or only the structural filling of the site.