Hello - wonder if anyone could help....

I'm having some work done on my garden which involves landscaping a bit of
it. The lawn wasn't that even and as there was quite a lot of soil left over
from some excavations my contractor suggested that the area was levelled.
Great - but I have a small concern - the levelling procedure was simply to
spread the excess earth over the existing lawn to a depth of between 1 and
maybe 10 inches - is that OK to do? Just wondering what the grass dying off
underneath the soil will do to the root system of any new turf overlaid on
top. Or is it perfectly OK to do this?

Many Thanks
David