I think it means what it says, "carry less."
I am using a cup of tea as an example.
You go out for an hour or two you can carry a flask, quite heavy and bulky but quick and easy.Anybody can just pour a brew!
You go out for a day or two, you carry the means to make a brew, a flask will not last long enough. This means, water, pan, stove, fuel, cup, and teabags etc. Most people can boil water and make a brew.
More than a couple of days, you wouldn't be able to carry enough water so you carry the , knowledge to find and purify water and (for example) a millbank bag, plus pan, stove, fuel,cup and teaabags etc. The weight of the purifying kit(and knowledge) is less than the weight of the water you would carry for a day. A lot of people could find water and make it potable.
A couple of weeks and carrying enough fuel becomes an issue, so you carry the knowledge to find fuel and prepare a fire, so now we lose the fuel we would carry and probably the stove. Not everyone( thinking general population rather than bushcrafters) has the knowledge to make a safe and efficient fire.
Extend this further and your lighter runs out, knowledge of primitive fire takes over, you run out of teabags and you start using your knowledge of flora to make nettle or pine tea.
So the more knowledge you have the less you
need to carry.
But I carry what will make my stay most comfortable taking all things into account including the time frame and the environment, this usually means the back of my car is full, but I guess I would trim down if I was walking the applachian trail, I would carry less and spend more time finding and improvising what I need along the way, I do have (some) of the knowledge but not always the incentive!