There is no valid reason NOT to be able to cut them back now, although a primary reason for planting OG's (at least to my eyes) is for their winter interest. But commercial landscapers and groundskeepers tend to work to a schedule of their own, often dictated by their clients' wishes. Tidiness and the general winter prep and clean-up that occurs at this time of year is probably motivating this action.

There was a long discussion of this same situation on this forum last season. Perhaps a search of the archives will turn it up.