is one piece episode 600 filler?

Luffy and his group are still being watched by Vergo and Monet. Luffy doesn't know Doflamingo but suddenly remembered him by Smoker asking him that he already seen him back at the Navy Headquarters.

Tashigi commented that Doflamingo attacked Moria after the War of the Best It then cuts to Caesar Clown entering the lab where Nami and Usopp are hiding the drugged children. The children are still going rampant due to the drug candy's withdrawal symptoms and one of them attacks Nami.

Usopp tries to attack Caesar, but fails.