I liked the article but I tend to see that defects get raised in these informal/formal early testing sessions. They get found early. They get fixed immediately. They often don’t get entered to the bug system. So the net effect I see is that the early involvers don’t raise as many defects when entering their formal testing phase.
The same goes when I get involved at a design stage. I can help the team to design out some of the defects I would riase when testing. Some are obvious, some not so. But being involved early allows you to air concerns and design decisions earlier meaning less chance of defects. It also allows you to lay down the types of things you’ll be looking for when testing which often results in programmers unit testing for it, designers and BA including more detail in specs/stories etc and the testers being trusted for their honesty, critical eye and ease of working with.
If only all testers could read this post of yours. It’s a great post. Lots of insight.