There is also the fact that Bostrom has been operating under extreme long term incentives for many years. He has been thinking (and being paid to think, and receiving grants and status for) the long, really long term future for quite a while. AI scientists on the other hand usually are more focused on the time of their lives, the lenght of their grants and other more mundane, shorter term considerations of the scientist life.

Most people have scarce to no mental representation of the World more than two decades after they die, I see no reason why AI scientists would be different.