Oh please for the love of all that is good in the world, yes, this! I'm playing on PC and one way or another I'm constantly fumbling because of the lack of precision in the mini-game.
I'm sure with a touch-screen it's effortlessly intuitive to play, but between the distance from the place I need to click, and the bars I need to watch carefully, I'm constantly either missing the target entirely, or accidently dragging to one side or the other while holding down the click, which plays the animation like it's milking, but then the bar starts sinking fast and panicked fumbling ensues. (btw the bars themselves are very well programmed, very responsive, never felt like they were out of sync or delayed in any way with the clicking!) I don't feel like the balance of the game is off in any way, at least for my reflexes, it's just that I can't watch what I'm doing and the bars at the same time.
Alternatively to hot-key inputs, two ideas that I had were since you lock out the right click during the mini-game anyway, remap it to be left click/right click for each side, or if that's something that is janky because of the V.N. structure the game's built on, the most direct and easy idea would be just make the entire left and right halves of the screen two inputs. Basically bump the hit-box size to the entire screen and the only need is for the mouse to be on either side of a dividing line.