Help

Hey guys, I’m new to turf. I’m getting my gardens ripped out and turfed with Zoysia. My question is, the guy doing it has said it’s fine to just lay the turf on the garden soil? I’ve done a bit of research and everything says I need a 50mm recess to meet the existing grass so it’s not uneven? Plus there’s a higher risk of it not bedding in etc. should I push for a recess to be dug? Apparently it’s not covered in the quote to dig a recess 🤷🏻‍♂️