I watched just enough of the St. Jude/ FedEx and saw the topic at hand for the first time. Is there a reason, apart from TV aesthetics, to spend time doing this? Is it being done at non-televised courses around the country or elsewhere?
Speculative, logical reasons:
1) It makes balls easier to find
2) Weed control
3) Person on rough mower suffered a medical emergency and thought he/ she was on a green
My cynical guess is someone deemed the vegetation that stands a foot higher than the surrounding turf isn't enough contrast, and could be prettier.