Being a little cynical the reason for the "unthinkable" thing may be in the article:
> “The government and the pharmaceutical industry have invested almost all their resources, and some of the brightest people have been in the amyloid area,” he says
Not so much unthinkable but if you speak that thought those invested may attack you in the political "grant applications have negative feedback" sense.
You see that quite a lot that when people have built careers based on hypothesis A they do not take kindly to the idea of A being wrong.
> “The government and the pharmaceutical industry have invested almost all their resources, and some of the brightest people have been in the amyloid area,” he says
Not so much unthinkable but if you speak that thought those invested may attack you in the political "grant applications have negative feedback" sense.
You see that quite a lot that when people have built careers based on hypothesis A they do not take kindly to the idea of A being wrong.