They might not be old enough for it to matter yet, and we might see numbers approaching that 67% as people live longer.

https://www.nia.nih.gov/health/what-causes-alzheimers-diseas...

"Older age does not cause Alzheimer’s, but it is the most important known risk factor for the disease. The number of people with Alzheimer’s disease doubles about every 5 years beyond age 65. About one-third of all people age 85 and older may have Alzheimer's disease." (emphasis mine)

Perhaps if we beat cancer and cardiovascular diseases etc and see human lifespans reaching 100+ years old, we'll see close to 67% of people at that age get Alzheimer's.

Maybe it's like prostate cancer in that it changes so slowly that often something else kills you long before the prostate cancer has a chance to? [0]

[0]https://www.cancer.gov/types/prostate/understanding-prostate...

I don't think one should extrapolate this study on a lab-grown human-like tissue to mammals like rodents in the first place. Extrapolation to humans is even more bizzare.

The article covers this question, they think it is just a factor. A funnel towards Alzheimer's that a lot of people still end up getting to the bottom of.