Yes, part is the fluff of it since there is no basis for why those classes should potentially be able to roll higher than everyone else. However, part of it is also that expertise boosts the numbers (resulting in the fluff issue) too much. We've already reduced expertise to a max +4 vs. proficiency +8, instead of +6 vs. +6, and when you read my (just above) post, I am probably going to remove the number boost entirely in favor for advantage. Other features, such as doing expert skill checks via bonus actions instead of regular will likely follow.I would never say that you're not entitled to your opinion; I'm just trying to get a straightforward clarification about whether your dislike for the rogue's higher ceiling (as distinct from the higher floor) is driven purely by aesthetics/fluff connotations, or whether there's also a mechanical problem you see with it. It's clear to me now, despite the straightforward clarification I was looking for, that it's driven by aesthetics/fluff. It's still your opinion, and you're still entitled to it. But it muddies the search for a solution if we can't be clear on that.
You've expressed an opinion that a 75% success rates on stealth checks is too high. I disagree, but I accept your opinion, and worked to come up with a solution that would lower that number (which is reasonably seen as question of bounded accuracy as the concept generalizes to skill checks) without taking power away from the rogue. But as recently as this morning you are still claiming that your issue with the rogue's higher ceiling, which is a separate issue except insofar as we can't distinguish the two using fixed bonuses alone, is about bounded accuracy too, which is factually untrue. What bounded accuracy does is keep success chances strictly above 0% and strictly below 100%; so moving a success chance from 0 to something above zero is working with bounded accuracy, not against it.
Except for looking for alternative solutions, I am still stuck with high stealth capability. We will see if other factors can mitigate that.