Wheel bearing torque

This is kind of a technical curiosity question.

So this weekend I repacked the wheel bearings on my utility trailer. According to the specs the castle nut is just suppose to be hand tight then the cotter pin inserted. If the hole to the cotter pin is behind a post on the castle nut you are then to loosen it until the pin can be inserted. This means that there is little to no torque applied to the wheel bearings. The wheel has extremely little play from side to side. The theory is that as the wheel spins it will heat up and expand. It's better to be loose than tight according to the specs.

This same day my brother came over to use my garage and tools to replace the rotors and bearings in his old Ford (Mazda) 4WD pickup truck. According to the specs we tighten down the tension ring to 150 lbs of torque after the bearing were in. I couldn't believe that. I thought it was a misprint of 15 lbs. Getting on the internet I found that it's common for many manufactures to be around 140-180 lbs.

Why would there be such a torque difference between my trailer and his truck? Essentially the design is the same. You have seats against angled roller bearings all packed in grease.