I will add to this confusion some of my observations.
Hiding at its very core is just telling your squad to keep their heads down (go prone) more often than crouching and looking around. Hence, you can still spot will hiding, just at a reduced effectiveness. I will also surmise, that given all other factors (experience, etc), a squad will fire on enemies in their target arc whilst hiding at a reduced effectiveness, the caveat being that while prone they can not see the target in the arc.
Being that the squad behavours of spotting and firing are no longer abstracted, each pair of eyeballs (height and facing) do make a difference on how many guns you can bear on a target.
I use the short cover arc tactic extensively for scouting. The team will spot objects further out than their range for sure. However, they may not spot that AT gun in the bocage line immediately, so the decision on how long to keep the scouts stationary is up to you. I've had previously unseen targets show up a minute or two later after laying still at my OP.
Nothing gives away a position like fire arms flash. This is why many scouts die so fast to be made useless. As this works both ways, if you are in a hurry, you may want to send some expendable 'bait' out to entice the enemy to reveal themselves to the scout.