We simply assume that the warrior is contributing their shots and blows to the swirling combat going on. This means we don't have to worry about whether individual models strike their respective opponents in base contact.
When a unit inflicts hits, they may only affect enemy models which are engaged with them or supporting a model that is in contact with them. These are the only enemies able to strike back at them, so it is reasonable that these are the only ones who can be hurt. If all the enemy models in the 2" 'Danger Zone' are slain, then any excess wounds are lost.
Diagram 6: The 2" Danger Zone extends around models engaged in base-to-base contact; only models within this zone can be hit by the combat's attacks.