I don't think it necessarily had to be a high fence to get up on a buck like that.
I've done nearly the same thing twice before. During peak rut a few years back, a big buck had just lost a fight and ran across a field right to my buddy and I. The buck was in a mood to fight and my buddy had his rattling antlers with him. I held them up to my head and walked slowly towards the buck and got within about 12 feet before got nerveous enough to leave the area.BTW - we were at the truck and had just put our gear away.
Another time, this last season, I was walking back to my truck yet again and came upon a button buck bedded down next to the trail. I didn't feel like shooting a BB so I decided to watch him instead. I was able to walk within 10 feet of him to get my gear back to my truck and get my video camera. Then went back and video'd this BB for almost an hour as he browsed on leaves, he and I walking slowly down the trail together.
I guess it depends on their mood and the perceived threat level.