Never take any one person's advice as gospel, that goes for your friend and myself. I highly suggest you start doing lots of experimentation on your future grows with side by side comparisons. I personally have tried all sorts of different training and leaf removal techniques and learned a lot in the process. There are a lot of smart people on these forums but there are a lot more idiots, always challenge anyones advice with real world experiments.
Yes, the sugar leaves are still producing food for the plant to grow but their surface area is no where near as large as the big fan leaves. They cannot produce nearly as much food/energy for further growth as the large fan leaves.
Does it take energy to keep fan leaves alive? Where do you think that energy comes from? That's like trying to lighten up a race car to make it faster by removing its engine and gas tank.
How long exactly have these plants been flowering for? Its really tough to judge but they don't look to be that close to being ready to harvest to me, but that could just be due to the fact I'm looking at these pics on my small cell phone screen and can't see much detail.