the quick answer is yes. they are advocating cat rigs. the longer answer is that htey are advocating rigs that bend off when they power up. i don;t have drawing software on this computer yet… so try this.
get a piece of paper, and draw a mast. just a stick will do. you are looking at the back of the mast. [if you want to get draw a sail you will get things more complicated, so wait on that!] now, on the right hand side of the paper, draw an arrow going towards the mast. that is the wind. the mast is straight up and down. now, make the arrow bigger. the wind just got stronger. the mast is going to react accordingly. draw the top of the mast bending away from the wind. the mast has just depowered. the leech of the sail is spilling wind, and becoming less effective. this is one form of mast bend.
now, new piece of paper.
draw a mast. this time, you are looking at the side of the mast. so draw a main sail on the mast. now, point your finger at the sail from straight above the picture. your finger is the wind. now, “pull” in the main sheet. the boom comes down, and the sail tightens. it also applies pressure on the top of the mast. [you might draw an arrow following the leech of the sail down fromthe mast tip to signify this tension.] now, as you tighten the sail, and put force on the mast, you pull it down. redraw the tip of the mast, so that it is bending back towards the stern. you have just depowered the rig again. the leech is spilling wind, and the sail is less effective.
now, last drawing.
draw the sail looking down on it. [this is pretty much a curve that looks sorta like an airplane wing.] now, thinking o the last drawing, bend the mast. when the mast bends aft, and pulls down at the tip, the front pops out forward. this pulls the leading edge of the sail forward, so do this on your drawing. as the leading edge comes forward the middle of the sail flattens out. the edge spills wind, the sail depowers.
there! now you know all there is to know about mast bend. [within reason that is] please don’t find this condisending, i had to put it very simple step by step terms to visualize for myself!
now, as for adding luff curve. that is a much larger topic. i would suggest Tom Whidden’s “the art, and science of sails.” really good book, writen by a nice guy who knows his stuff.