Not in all cases. It depends on the placement and how you're stacking it with other oCDs.

For example, running 670+ SS, you can set it up so you delay the 2nd application of BFB by 1 GCD (So before PH), but ensure that the BFB is used half way through your GCD and ensure you have buffed DoTs on both leg and straff doll. By doing this, and ensuring you've hit all of your jumps 100% of the time, you can set it up so you can land Jump just before the BFB ends, without delaying the PS + Jump before it.

There's other things you should be doing on A4S. If you're on Leg 4 for example and want to pad a lot of DPS, you could delay BFB by a few GCDs so you can get x2 BFB buffed GKs on triple targets. Leg + Staff + Add next to leg.

What you don't want to do, is hold BFB for multiple GCDs like what most people were doing in A3S progression for the Hand of Pain Split, and the Healer Snatcher.