Growing wine at a Jewish Cemetery permitted?

I am working on a documentation of an old Jewish Cemetery, established in 1626 in Southern Germany and I noticed that a member of the mainly Russian Jewish Community cultivates vines at the cemetery. Can it be true that growing wine at an old Orthodox Jewish Cemetery is permissible or isn’t it so that we are not allowed to have any material benefit from a cemetery?

The only things that are prohibited to benefit from are the parts of the grave that were originally detached from the ground like the tombstone. It is permitted to collect fruit from trees that are planted in a cemetery, as long as it is not planted on the grave itself. [שו"ע יו"ד סימן שסד וסימן שסח סעיף ב].