Sadly, this has been my experience as well. IME it isn’t just the size that changes from year to year but also the cut. My Attack Pants from 10 years ago were sized perfectly. Then I added Attack Pants ~5-6 years ago and they are both smaller overall and a bit slimmer cut. Ordered another pair when they were on sale a few months back and they are super snug in the waist and fuller-cut everywhere else.
It’s a shame really as I really love their fabrics and their field performance is usually excellent. Going on a Sheep Hunt in August and getting in shape so I’ve lost a few pounds and the Attack Pants from 5 years ago fit the best and will be coming along. Agree that their sizing certainly fluctuated over the years, but I still just love their clothes too much to throw in the towel, and just deal with exchanging what doesn’t fit. But try it on shortly after receiving as they only allow exchanges for limited periods.