You are correct insofar as higher tyre pressures will lighten the steering, but there are a number of other factors involved too.
What state are the steering link and track rod bushes in?
Are the kingpin bushes in good order? Are they correctly greased, including the underside of the bronze thrust pad?
Is the tracking, camber, and toe-in set correctly?
What about the size of the steering wheel? A larger wheel will give significantly lighter steering.
