Forte's worried, after Phantom going boom, that the others could follow. Fafnir is more likely to take a fight further than he should and game Zero doesn't care about them so he'd probably finish him off.

"So the soonest we can reach Phantom would be with the place with the bombs. At least that gave them a little more control over the location. "He's still the last of them to show though, so if were trying to get the code to them, we should focus on the others." And maybe doing so would get the code to Phantom sooner anyway.