Trucks are so weird right now. I just tested on the same spot when the patch was in Exp. You can make that climb, but you need to use traversal and disable vehicle assistance. Keep it in 3rd as you go up and drop down to 2nd and 1st as you lose RPMs and traverse the steepest parts. 'Bonfire hill' near Morton is another good spot to test hillclimbing.

I think this is a good example of the "truck has no power" issue. Vehicle assistance does play a role, as does technique, which leads to different players having vastly different experiences.