Yes, I think you are right on this. I grew up with a brother who regularly smoked pot and acted like a crackhead when high. He was NOT mellow and he was NOT nice when smoking and he smoked it all the time. It was one reason I left home young.
My parents did attempt to control him to no avail. Nothing worked to stop him. While in high school he was arrested over 20 times, and averaged 5-10 arrests a year after that for the first 10 years after high school. It wasn’t until I got out of college, that I found people who could smoke weed and just get mellow.
My brother did achieve one good thing. His behavior forever made me NOT want to do any kind of drugs and I never did.
I hope your brother is still alive.
The mellow pot thing is very common, especially among the middle class types, but pot is a real drug, and it did not come from the middle class, it came from where it still is common, and is still the dominate drug, the violent black and Hispanic underclass.