Michiko (美智子 ) , born Michiko Shōda (正田美智子 , Shōda Michiko ) on 20 October 1934, is the Empress of Japan as the wife of Akihito, the current Emperor of Japan reigning from 7 January 1989. She succeeded her mother-in-law, Empress Nagako (Kōjun), consort of Emperor Hirohito (Shōwa).
Michiko Shoda succeeded her mother-in-law, Empress Nagako, as Empress of Japan upon her demise in January 1989. 
It's neither correct nor incorrect because she did succeed her mother-in-law, but not upon her death (which was in 2000).  I think the verbiage "demise" confused the AI, especially because it is surrounded with factual listing of details which would take precedent in the accuracy algorithm. 