I have only limited experience so far, but from I gathered the scenarios are designed around the party moving around as a whole. Scouting ahead even at a short distance gets you into some pretty hairy situations because the encounters seem to be 'waiting for the party' instead of doing their own thing according to their own schedule.
There is a good reason behind this, it's very hard to follow everything happening around as a GM if you have to keep 7-8 encounters in your head, each with their own timetables and schedules and stats. Doing it the way its done now is more cinematic - let's not kid ourselves, the system is designed to cater to needs of diverse groups, players and GMs. It has to be simple and straightforward, otherwise we'd be elbow deep in conundrums.
If someone does scout ahead and they're doing it well, try to add some little hooks into your storytelling to let them know about some parts they might be missing. If they chose to ignore those, fine, they had a choice.
It might be something as simple as hearing a human whimper from a corridor to the side (a prisoner at the end of its strength), or some strange markings around the trap pointing out to a different use of it, or if your party just stealthed past an important encounter you could have one of the goons go out to head to the toilet and the party basically catches him flat-footed and out of reach of his friends - in a way you just rewarded the party by splitting what would otherwise be a difficult encounter into two smaller ones which are not nearly as difficult. This I feel is a pretty good reward for a well executed scout ahead maneuver.
Scouting ahead does carry a huge risk with it, and scout can often end up dead and the party split - but if it's done well it definitely deserves a reward instead of a penalty.
