I don't think Charlesworth had much experience planing edges by hand. I watched a video in which he planes an edge and ends up .002 hollow and then says "I consider this straight" Really? Can you imagine trying to do a rub joint with two such "straight" boards?
Then he says "I think its a remarkable tolerance for a hand tool on timber". It is not remarkable; it is pitiful. It is reasonable to expect no light to be seen under a straight edge. There is no point in having a Starrett straight edge if you are not going to use it.
https://www.youtube.com/watch?v=vqPP6-0jkws