18% by the American and Medical standards is considered ideal......(or sub 17% is at least)....and yes I imagine trying to get down from 18% with GPP will reduce strength and have some muscle loss.
I think trying to sell the idea of a 6% BF person who can DL 600lbs, run a 5 min mile, have a 2 min Fran, huge Biceps and be the best at everything is an unrealistic view that most people coming into CF imagine they can get. I think that's his point too.
That reminds me of when it all hit home a long time ago watching one of those strongest men competition. Of course lots of backwoods lumberjack types with I imagine over 18% BF but some serious muscle too...and then the US guy is a oil down tan bodybuilder who pretty much looked like he just came from a show....very impressive and looked like he should of whooped everyone by his sheer muscle definition and size.......he came in dead last....every event...that is the ones he could finish.