All he said was the pressure seemed high compared to a car tyre. The unnecessary disastrous willy waggling argumentative my physics degree is better than yours tangents this place trails off into are amazing.The confusion started when the op mentioned "car tyre". It simply isn't a car tyre it's designed for many purposes and Ifor Williams chose it to be fitted to its small trailer probably in conjunction with one of the tyre manufacturers. I'm guessing the 'c' rating on the tyre has a big bearing on its specification.
Forget the laws of physics with this stick to the trailer manufacturers recommend tyre design for the trailer in question and the pressure from the charts.
The required tyre may look similar but will have different compounds, wires and wall thicknesses to the equivalent car tyre it won't be designed for comfort and grip while cornering or braking it will be designed to carry the stated load with little flex at the stated pressure to save overheating and failing at the required speeds.