Is “Happy not to think of Shu” true?

attested in history

According to the Han-Jin Chunqiu quoted in Pei Songzhi's annotation to the Records of the Three Kingdoms, Shu Shu, Biography of the Later Ruler, Sima Zhao asked Liu Shan if he missed Shu, and Liu Shan replied, 'I am happy here and do not think of Shu.'

Liu Shan

In official histories, the later ruler of Shu Han is portrayed as obedient to his father's will, feigning ignorance, or simply mediocre.

Other claims about Liu Shan