I am one who loses a lot of hair when I cowash. Whether it's due to the extra manipulation or some other reason, the fact remains that when I cowash, there is a lot of hair in the drain. When I use shampoo, there is much, much less hair in the drain. I've used lots of different conditioners to cowash. I still lost a lot of hair. I even recently tried cowashing again for about a week. Lots of hair loss again.
2C/3A, fine, normal porosity.