Earlier quoted context omitted.
If it's operated by a mouse you're not sure where to click and hold, and how it will react when you move mouse in which direction. I assume you're using it a lot and then it's intuitive. For novice it's not. If I click on bottom part will it operate in another direction compared with clicking on top part? Or what about if I click on left or right edge? Can I also move mouse up-down and left-right or is only one direc…
Yeah, I see how it can be confusing for novices. But learning curve aside, there is something other than just looks that kept this UI pattern alive all these decades. How I see it [1], absolute values don't matter audio software, except when working with loudness compliance or some very technical things. What's important is how things sound, and it's generally a bad practice relying on UI metering to dial in sound in…
The shortcomings of sliders you mention are down to shitty implementations. I have never seen a slider that resets if you click in the middle of it; that's a crap UI. It's common to simply have a little reset button next to a variable control.
"should horizontal slider change its value with up-down movement? should interaction range extend beyond slider length?"
Of course not to both. I've never seen either one of those behaviors.
Knobs are bad for fine adjustment, because the closer to the center you click and drag, the more drastic the adjustment per pixel of dragging.