You really can't compare Brook providing the salt to Yamato freezing the bombs. Brook knowing about the salt was the only reason the crew was able to actually beat any of the zombies. The bombs were a plot device to take down Big Mom
Especially since I don’t recall the salt actually being all that useful. The two main enemy zombies were Oars and Ryuma, neither of whom was actually defeated using salt. Luffy got everyone’s shadows back by beating up Moria, not using salt. They didn’t need salt to beat Absalom, Perona or Hogback.