I don't buy it. I raced as a skinny climber. The constant little and not so little accelerations of a competitive race took its toll on me. Having very light tires and rims were a Godsend. Being able to very quickly jump up a few MPH to grab that wheel going by or pulling out could save chasing hard for 100 yards. Making the break vs falling 3 feet short could be the difference between top 8 and 25th place 10 minutes back.
Now if you are strong enough to make those repeated jumps on heavy wheels, its a different story. (The big, strong guys couldn't ride the light rims I did unless they had an endless supply of sponsored wheels. 290 gram Fiamme Ergal rims and 250 gram silk tires. (Yeah, everyone rode those tires. My budget didn't allow me to ride Seta Extras. But I could get two seasons out of the Ergal rims on New England roads.)
Ben