[ Frontal knows prickly teenagers and he does not care in the slightest that Keith is not bothering with all the polite formalities. They are having a casual lunch together here, it's fine.

It's not like Frontal has ever had a casual lunch with anybody before, so for the first time this is going decently well. ]

Nothing of the sort. "Full Frontal" stands for having nothing to hide, though "full frontal assault" is certainly not a bad association either.