During the prologue of the Giro Team SKY was seen using bare HED rims rebranded with PRO logos and relaced to Dura-Ave hubs instead of the normal HED Sonic models. Team SKY went through all this trouble because they're sponsored by Shimano (PRO is a Shimano company). I remember when HED3 rims were all the craze, and stupid hipsters were cracking them like no other. I wonder why? OH WAIT, maybe because they're made of carbon fiber and not meant for tricking. How about you actually ride your bike?
Shimano's deepest section rim is 50 mm, while HED's deepest is 90 mm. What difference will 40 mm make? A lot in time trials. The more aero the less drag yada yada yada.