So bad soil causes thatch. But not if ryegrass is growing on it?
Or does excessive nitrogen cause thatch? How much nitrogen? Does compaction cause thatch--if so how much compaction?
To me thatch is a sign of an aggressive cultivar of Kentucky bluegrass...doing what it is supposed to do...get really thick.
Power raking is fine--if the customer believes it will cause quicker greenup in spring. (Probably will not). The brown appearance of certain grass types probably reflects the slow spring greenup of certain high-quality Kentucky bluegrass cultivars...which will look truly excellent later on.