Erm...that's archer using broken phantasm.
Archer's true potential is not using bow and arrows, but his reality marble--which allows him to trace any swords by just looking of it, ignoring all process of tracing socery(Apprasial Creating Concepts, Imaging Basic Structure, Copying Construction Materails, Imitating Creating Process, Resonating Experience of Weapon, Reappearance of Time).
(Quoted from Fate/Stay Nigth day 11)
Anyways Archer's close combat style of fighting is just...the way he liked it. In the Unlimited Blade Works Scenerio where Archer was alone against Lancer he STILL fought with those two swords.
There's also a time paradox to Archer's fighting style.
As we all know
Also, against berserker, Archer's bowmanship can actually kill berserker. Which, is also seen in Unlimited Blade Works Scenerio. (Archer destroyed the whole graveyard along with one of Berserker's life in one hit...scary...)