I'm sure you are correct, but I have not had a rain jacket, cycling or otherwise, that I could put in any of my jersey pockets. If it looks like rain, I put the jacket and pants into one of my front panniers where they are easy to reach.

When I'm not using front panniers, they go under the bungees on the rear rack. I usually decide in the morning before I load up the bike whether to leave them in the rear panniers or put them where I can get to them. I have been fooled