I'm not sure there are relevant units here for most drills. Most drills just have numbers from 1-n regardless of how much torque they can put out. There are calibrated torque drivers out there that can limit to a specific torque, but most hand drills just seem to have a relative measure of torquiness.
I am willing to bet that this change would achieve approximately nothing.
The people who have a mental model that allows them to understand what torque is and how it matters for drilling are the same people who will already know it's controlling torque, specifically torque of the head, controlled by a clutch mechanism. Nothing else makes sense.
And therein lies the problem of believing "good UI will solve everything". It will not give you an understanding of the problem domain. And an understanding of the problem domain will obviate many UI needs.
It's also because the UI of that drill is shitty.
They should write the words "TORQUE LIMIT (N*m)" next to that dial.