Which is why the d20 sometimes isn't granular enough. 5% of the time? Maybe too much. 1% of the time? Hell yeah.Accidentally thudding like an elephant or stepping on a stick isn't something that should always happen 5% of the time, IMO. It should be something that's a possibility when it's dramatic (i.e., when you need to roll), but for everyday usage, nah.
Not quite. To me, you're rolling for it if there's a chance you might notice it even if you're not actively trying to. Plan B is the DM can roll in secret, but this is one where I like to keep the players guessing by having them roll and, should the roll fail, then not telling them what they just rolled for.See, to me, if you're rolling for it, then you're trying to notice it. And if the GM wants you to notice it, they might as well just tell you without the need for a roll.
And whether or not the DM wants them to notice it is (or should be) irrelevant to whether or not they actually do notice it in the fiction; and that's what dice are for.