If he is maintaining the greens on the dry and maybe lean side you are probably looking at old (spring) aerification holes or Graden lines. They become visible under these conditions. Basically, more oxygen is getting to those plants. Larger spots could be the segregation of the different types of bentgrasses, someone stated they do not have a monoculture. These patches are genetically different but are still bentgrass. This is how new and improved types of bentgrass are developed. Rumor has it, A-1 and A-4 where found on Augusta’s greens from segregation. Have you ever noticed the different color patches on your bentgrass greens during late fall, winter, and early spring? That is segregation. Not a big deal and neither affect playability. I’m the thread killer so I guess this topic is dead.