Hed helped start the wide rim phenomenon. It made sense to them: wider rims are more aero and have lower rolling resistance.
The minimum-recommended tire width is 22mm. In terms of aerodynamics, 23mm is ideal. But you can easily run any with tire here and get a better contact patch, great for sticking to the ground and great for rolling resistance. It's hard to argue with putting more air between you and the ground; it soaks up bumps and smoothes the ride, no matter how stiff your frame may be. That they come with a recommended max pressure of 100psi and maximum rider weight of 225lbs should tell you as much.
But the aerodynamics are equally impressive. By pairing a 6+, aka 60mm deep front, with a 9+, a 90mm deep rear, you get disc-like aerodynamics in back with a front wheel, thanks to Stability Control Technology, that plays very nicely in crosswinds and is still incredibly aero. The 18/24 build, resulting in a 787g front and 1035g rear, give you a wheelset that is great for time trials, criteriums, and flat to lightly rolling road races. Even smaller riders should be able to put these into their tri' bikes and have confidence no matter which way the wind is blowing.
Looking to the future and realizing that customers want more tire options, they redesigned their bead dimensions as well as their rim strips. The bead has been designed to allow tubless tires to better lock into the rim walls and the rim strips fits incredibly snug in order to keep in air and sealant. These wheels are tubeless-ready, so if you're partial to tube-free riding, you're all set.