So what you are saying is that the party can be never sure about traps? Is the trap-finding-skill the only skill in use with which the results are alway uncertain? How about crafting a weapon? Do you roll the dice for the players as well, because, you know, the swords that weaponsmithing PC made can always brake, he can never be sure?Usually in a case like this, the DM rolls.
Does a rogue in your game world never actually have a chance of being absolutely sure that there is not a trap where he or she searched? After all, the DM rolling for search traps is stadard operating procedure and whatever the DM says the result is cannot be counted on. To me, that is a really weird concept.
And it does not lead to a better immersion at all. All it leads to is that several members of the group look for traps. Continiously. Because if 2 or 3 people do not find a trap, chances are much higher that there actually is no trap. The game turns into a trap-finding fest.
Fortunately the rogue can do other things but find traps. Sneak attack and scout and maybe know his or her way around a city. But the last time I checked, the class chassis of the rogue securely included finding traps and being able to deal with them. Obviously in your game this is not the case, because the rogue can never be sure that he is actually proficient with this skill. He just never knows. Neither does the player of the rogue.I'm sorry, but I'm having a hard time taking this seriously. Are you suggesting that there is nothing that makes a rogue a valuable contributor to the party if he doesn't roll a natural 20 while searching for traps? Because I can think of tons of other functions for the rogue. Scouting ahead, sneaking away, trailing a mark, opening locks, skills in general (thanks to Expertise!), etc. In combat, you've got sneak attack.
Seriously, I have rogues in my campaign who have never checked for a trap, yet they seem quite functional and useful.
Do you do the same things for perception as well, finding hidden things and people in general? Because that decreases the amount of stuff the rogue can securely do in the exploration pillar. I do not find this concept to be very convincing. Especially not with the argumant of immersion. I get the feeling the basic skills of my rogue are nerfed in your game. You can play with this setup, of course. But a nerf is a nerf.
Comparing the general use of the trap-finding ability to reading an entire module and then having problems not basing decisions on that knowledge is taking the whole question too far. You are comparing apples and bricks.Improved immersion. However good your pcs are at playing down what they know vs. what their characters know, it does make a difference, at least for every group I have ever been in. For example, if I play through a module that I've read, even if I consciously avoid acting on that knowledge, then I simply know too much about what is going to happen to enjoy that module as fully as if there were surprises in it.
Oh yes, fudging is indeed a long standing tradition for many DMs. But it is a tradition that causes all kind of problems. And I have yet to experience a DM who does not fudge against the players. And it is always to make the game "more interesting" or "fun". Of course DMs fudge in favor of the PCs. But even that still amounts to taking away agency from the players. I rolled that 1, I have to live with it. That's what rolling the dice is for. What do you tell the players if you fudge against them? "Oh, the monster should not have hit you that hard, but I thought it would be more fun if it did and that's why I turned a 2 into a 14." Oh, you defeated the monster, but I fudged in your favor. Do not feel that you haven't earned that victory. It was just a little fudge....".Absolutely not- if you're the DM. Fudging is a time-honored tradition. Not every DM does it, but almost every DM does it once in a while. And in my experience, it's almost always in a way that favors the pcs. Personally, I really avoid it; I don't think I have fudged since around last Christmas (and this is averaging 2 to 3 sessions per week since 5e launched), and I almost always roll in the open. Nonetheless, I roll things where the pcs shouldn't know the dice result out of sight, including many Perception and Insight checks and some other things.
If a player 'fudges', on the other hand, it's straight up cheating. There's a different standard because they are in a different role.
To each their own but I do find the game to be much less exciting if there is fudging involved.
It is also funny that you expect the players to trust in the result of you dice rolls for the players if they know you fudge (in their favor or against them). Sorry, but to me, this whole concept stinks.