You probably got it from me a long time ago. I used to use wazine first, until I found out that it acts as a flush getting rid of large roundworms. If there's alot of roundworms in the digestive tract, the wazine could cause a blockage which could kill a chicken. That's why I recommend valbazen first. The worms are slowly killed and digested over 3-5 days, not all at once like wazine.
It's true that over time our knowledge increases and our approaches therefore change. What you say is very logical, but it then begs the question "why use Wazine at all if Valbazen kills roundworms as well?" Is Wazine needed to get any roundworms that the Valbazen may have left behind, or is it better to alternate treatments to avoid resistance developing?