At the beginning the vid shows all carbs are in good sync.
I revved it then let it back to idle to "set" the linkage and be sure they were still in sync.
Then revved to 3k rpm to check sync. The reason for this is to get an idea the condition of the linkage.
Your sync will most likely be thrown off at least a small amount because there is always going to be some wear.
Then let it back to idle to see it settle down all even.