I often throw broken bales at hay making over the fence to my Highlands and they eat them without problems, but ultimately it is your choice. I also let them in on harvested fields as soon as they are clear to mop up any hay that the baler has missed.
Well made hay should not be much different to hay that is months old. Years ago hay would have been made into cocks (small heaps), then put up onto tripods when it was still quite green and damp so I think it would have been dangerous to feed that for the same reason it is unsafe to feed lawn mower clippings (apparently it continues to ferment inside the horse). I'd say, if it is fit to bale it is fit to feed -- but if you kill your horse, don't blame me!
The old rule was, I think, that you didn't feed this year's hay but that seems to have all changed. Now old hay is rejected for some reason. Last year I fed some 4yo hay to clear the barn and the ponies loved it.