If you read the article thoroughly it explains exactly why your reasoning is incorrect.
Tldr; comparing control group to acceptors group is not right because who accepts and who doesn't isn't random.
We don't know the exact bias introduced but the author theorizes that people who are at higher risk are more likely to accept the invitation(e.g. someone with a colon cancer in family, someone having weird feeling about her tubed as the article calls it., etc.)
You are both right. The study at only 10 years didn't run long enough for us to expect to see much. That is one reason medical studies are hard, we are often interested in changes we could make today that won't matter for decades.
Tldr; comparing control group to acceptors group is not right because who accepts and who doesn't isn't random.
We don't know the exact bias introduced but the author theorizes that people who are at higher risk are more likely to accept the invitation(e.g. someone with a colon cancer in family, someone having weird feeling about her tubed as the article calls it., etc.)