Keypress/Boundary to ensure 'rubber-banding'?

I don’t know whether it’s something to do with my input device (or my own input ‘style’), but if I try to ‘rectangle’ a selection (otherwise known as ‘rubber-banding’), it only works if I start a certain distance from the staff lines (1.5 spaces?). Any closer, and I just select the entire bar’s contents.

Is there a way to ensure that I trigger a selection rectangle, or to reduce the distance outside the staff at which a click will select everything in it?

E.g. In the example picture, clicking, holding and dragging inside the red lines will NOT produce a selection rectangle, but just select the bar’s contents.

You’re right that there is padding of one space above the top staff line and below the bottom staff line, which you cannot change at present.