I don't think so. To me it looked like he was shielding his eyes from the flashlight. I suppose they can use flashlights and tolerate the sight of indirect light, but can't stand it when a beam of light shines directly at their eyes. That's my theory anyway
Yeah, it might be so... You're probably right!
But what's the idea then? There's nothing to scare about: Just flash the light on and they scare it, take barrel, throw it at them and when he's unconscious, just run away.
Is that it?
Dunno, maybe the sight of light just stuns them for a moment, then their eyes re-adjust to it. I'm sure Frictional will make them scary and threatening enough.