My parents own a small vineyard near bordeaux. We don't use weedkiller so there is grass all over (see http://montjon.com/). But no grass or brown grass doesn't necessarily mean that the owner uses a lot weed killer or insecticides, there are other ways to remove the grass mechanically. e.g. this type of tools https://youtu.be/gmaIugbRPDI?t=227

The video is convincing, but in practice it takes a lot of time and breaks many roots, so it's not ideal.