A dull knife does not only take more force. It takes your line with it.
Sharpness is not a property of the whole blade. It is a property of the very edge, measured in how wide that edge is where the two bevels meet.
A sharp kitchen knife has an apex a few hundred nanometres across. A dull one has been rounded over to a few microns. That is a difference of roughly ten times in the width of the part doing the work, and force concentrates on area, so a rounded edge needs an order of magnitude more push for the same result.
The part that matters for accuracy is what happens before the edge bites.
A sharp apex starts cutting on contact, so the blade enters where you put it. A rounded apex has to deform the surface first, and while it deforms, it slides. On anything curved, a tomato, an apple, a shoulder of meat, it slides downhill. The cut begins somewhere other than where you aimed and the error is already baked in before you apply pressure.
A dull knife does not make a rough version of your line. It makes a different line.
Pressing straight down relies entirely on the apex.
Drawing the blade along its length as you press brings the edge's microscopic serrations into play, each catching and parting fibres. That is why you draw a bread knife and why a long draw cuts cleanly through tomato skin at a fraction of the downward force.
For a straight cut, one long draw beats several short saws. Every direction change is a chance to leave the line.
A narrow angle, around 15 degrees per side, is keener and cuts with less force. A wide angle, 20 to 25, is blunter and survives contact with bone and boards.
Japanese kitchen knives sit narrow, European knives wider, cleavers wider still. There is no best angle, only the right trade for what you are cutting and how often you want to sharpen.
In Halfsies there is no dull blade to blame. The cut lands exactly where you drew it, which leaves your eye as the only variable and the scale as the judge.