Another funny thing about fiddly bits in game models is that they so seldom work the way they do in real life, when you consider the result of the fiddly mod on the chance of success.
It seems to me a lot of minor edges in skills are binary in effect. If you know the edge, or have developed the knack, or spent a bit of time on the technique--then the rest of your skill in the field can be applied in certain circumstances fully. And if you don't, it can't, or is much hampered. Such things act, in real life, more like "proficiency" than a minor mod. There is a sense in which being an expert or master or guru is having a somewhat complete set of such things.
For example, late in her life, we finally figured out with my grandmother that the way to learn her techniques was not to ask, but go do the thing while she watched, and have her correct our techniques. Because she assumed so many little things that she didn't even think to say. I was rolling out dough for shortcake, and she offhandedly mentioned that I should flip it upside down and rotate it 90 degrees halfway through. This would cause it to roll more evenly and not stick as much. This took her all of 15 seconds to teach. No one else in my family knew it, and everyone in it cooks. There was a lot of little things like that, and precious little that was major all by itself.
Now in a game, that isn't even worth a +1 to "cooking", in any system. Yet, if you know it when it applies, it is a major situational improvement on your success rate. I suppose traditionally in games, this is where a lot of the variance in the d20 roll is coming from--you know some such things and not others. But of course that is the wrong place for it, if you do the same thing over and over.
"Let it Ride" would make the d20 range make more sense here, assuming you don't mind retroactively including such explanations. If I sneak into the goblin camp and roll a 5, I didn't know something critical, even though I'm a decent sneak. If I roll a 15, I did know it. So that is why I can now sneak through the whole camp with that one roll.
However, that also makes me wonder about a really simple, modless mechanic. All skills are handled with a d6. Roll the right number, you succeed. Your needed number is:
1+ auto success, anyone can do it, or your opposition makes it that way
2+ the problem might sneak up on you, but probably not
3+ you've got a definite edge but not definitive
4+ evenly matched
5+ the problem/opposition has a definite edge
6+ you might get lucky
The mods are all major things that can shift the ground. I need a 6+ to hit the halberd master, but make him fight on ice while I have special shoes, and we can move it. Or you might extend the contest to multiple tests, preferably some that aren't so tough.
What makes this mechanic interesting to me from a feel perspective is that the odds of those things are mostly pretty close to how I would expect, given the descriptions. If two opponents are evenly matched, then 50% is about right, not the 2/3 or 65% that feels better. But if one side has a real edge, then the 2/3 success makes sense. It breaks down on the other numbers for single checks, but not for a series.