Most of the barns in my area don't specify exactly how much hay is fed per horse because it will vary. Easy keepers will not need as much as your average TB.
Most barns around here either specify free choice, unlimited OR how many hay feedings they offer per day. I've never heard of anyone actually stating they feed 2,4 or 10 flakes a day. If they did I'd be concerned because I dont' subscribe to one size fits all horsemanship