You don't have to believe me.
I do not believe you: You are saying that you are an experienced grower and you don't think yield of the ones in mentioned are possible?
Check out
@Renfro 's grows for example.
And why would it not be possible with a 100 Watt HPS lamp to get a pound? If you veg for a long time, top your plant several times, scrog, and just keep the light on it long enough... at a certain point there will be a yield of a pound. It probably will look not the best with horrible foxtails, and the veg time will be extremely long, but it will work.
But if you don't think it is possible... also ok. It is a free world.