No, they didn't. The reason is to let the soil settle. At the moment we have just stones, soil and weeds. So turning it over, levelling it and letting more weeds grow would actually be an improvement. I know more weeds will grow, my reason for killing these is because the whole area is thick with weeds that have had years to establish before we built our house. It just means removing less weeds later (ones that aren't as well established and deeply rooted) before laying turf. It's just saving a bit of time later so the majority of the hard work is done (levelling). I understand that some might advise kiling all the weeds at once.