The assumption that if there are traps getting hit by even one of them is necessarily more punishing than the rogue being surprised in combat 100% of the time is pretty much just a reflection of how occasionally D&D has instadeath fuck you traps.
More generally the optimal choice obviously depends upon the frequency of traps as well as how threatening they are compared to the frequency of monsters compared to how threatening it is for a party member to be caught off guard by them.
There are traps in D&D that aren't very threatening, and you'd be better off with the rogue soaking those so he gets to go in the surprise round so he can chuck a bajillion flasks with sneak attack to instantly wipe out a threatening monster.
It's funny you should mention that, because I've been known to freak people out by immediately dropping into a guarding stance whenever I'm distracted from a technical activity by a loud noise.
That time it takes you to drop into a fighting stance is all the time it takes someone good to knock you the fuck out before you are in that stance. Of course, in D&D surprise is more like a few seconds advantage since there aren't many useful actions smaller than a standard action. Obviously from a less abstract viewpoint, this is silly.
I've actually done enough martial arts training to tell you that if I'm reading a book and someone surprises me, they get hit before I even know what I'm doing. It's actually a common thing among trained fighters.
Heck, I've even been known to reflexively put people in armlocks because they started splashing water at me in the pool.
Of course, this still means that you have to convince me that finding traps is like reading a book and not like paying attention to my surroundings. I mean, can you honestly say that when you are looking for your keys in your room you can't notice when someone walks in?
Paying attention to your surroundings is a skill that you can learn to multitask if you really want to do it. The problem is the most people don't because it has no value in our society.
If someone good at jiu jitsu gets behind you, you have probably lost. Rear naked choke, fuck you. Or maybe the first contact they make is a knockout blow. And it's a hell of a lot easier to do that to a guy who's guard isn't up. Your situational awareness does matter against anyone as competent at combat as yourself, because they will have a fraction of a second advantage on offense, and moreover will be more able to anticipate your defensive move because they are looking at you properly whereas your attention may not have been initially focused on the proper part of their body for prediction. Professional fighters have lost matches because they were a quarter-second slower than their opponent.
Your "I can hit them first when they have no combat experience because I am a l33t fucking shaolin master" is a load of horseshit. For anyone of sufficient skill, getting to strike first is a huge advantage. And they will have it if you are sitting in a chair, reading a fucking book. If the bullshit you said was true, it would be basically impossible to KO someone with a kick to the head because that pretty much depends on failures in the opponent's reactions or predictions. And notably, that tactic can work when people are in full combat mode staring at each other from 5 feet away.
And this is neglecting the fact that if the rogue is staring at the cracks in the goddamn floor looking for traps or hidden passages, he isn't gonna see the crossbow bolt coming from thirty feet down the corridor. Because he is looking in the wrong direction.
Now, I'm not saying I actually like Swordslinger's system (I don't dislike it more than the current system either, and I don't think it's enough on its own to make traps interesting), but your verisimilitude complaints are retarded (this does not reflect upon the fact that in practice, I expect parties to pull exactly the bullshit you say they will with bullying the rogue to be in constant search mode even when it's suboptimal, thus pissing in the rogue's cheerios).
I'd rather traps of the "search the walls by eye" form were constrained to low levels and had more minigame stuff going on. The trap minigame could be more serious and involved (but abstracted, sort of like hacking minigames can be fun but they are abstract). Rogues could lay down quick traps or they could mess with an existent trap by moving the trip wire, changing the height the secret crossbow bolt comes out at, making it so that the normal safe way to disarm the trap triggers it, etc.