Some consider Mizuta's attention to detail trite, and certainly for him it's an exhausting exercise while maintaining pace and interest, but when done correctly it adds a lot to the realism. That being said, I had a hunting partner who didn't hear my unsuppressed .30-06 rifle when I shot a doe near my position, which was about 500 yards from him. That gun's loud as hell, too.
If the guy who stabbed the Khukri monkey is 10 mins way, he's probably further off than that. The dense forest also mitigates sound and light. Yes - especially with short silencers, carbines, and supersonic ammo - you will have some sound and a small amount of flash. But not enough to see in the brush not enough to hear from that far away. Discount Wick is pretty damn good, though.