Based off how "bright" they seem to be in your mirror, those probably aren't the high beams, especially if it is a Cascadia that was made in the last 5 years. It's gotten harder to tell when someone actually has brights on, or when its just their normal headlights. I rarely ever use my brights, and I don't know how many times I've been flashed by people who think I have them on. Sometimes I kinda wish I could hear their reaction when I flash mine back at them.

There are a lot of people in cars that drive with their brights on too though, it isn't just a truck thing. The big problem though is that truck headlights are at a great height to directly shine into the back of small cars, which ends up making them seem bright compared to smaller vehicles.