This can also be applied to "Denryaku" written by FUJIWARA no Tadazane of the regent house of Fujiwara and "Gonijo Moromichi-ki" by FUJIWARA no Moromichi, so it seems that the regent family were not particularly adapt at Classical Chinese.
これは同じ藤原摂関家の藤原忠実による『殿暦』、藤原師通による『後二条師通記』にもいえることで、摂関家は漢文についてそれほど得意ではなかったようだ。