They use a 4-tube water manometer to synchronize a TINY amount of vacuum bled off the venturi. Kawasaki, Suzuki, and several other 1-barrel per cylinder bikes use a similar system. I think the designers of those carbs have a secret agreement with Jim Beam, Jack Daniel, and Jose' Cuervo to boost sales of their products. You obviously haven't tried to make a living synchronizing multiple carbs. Everything works well on paper.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!