What does it mean to say that Fei Fu is proficient in Confucianism?

This sentence comes from Song Gaozong Zhao Gou's Chronicle of Momo. Zhao Gou is good at calligraphy. He is good at truth, line and cursive script. His brushwork is free and easy, natural and smooth, and won the charm of Jin people. Mo Hanzhi is a book theory by Zhao Gou, which advocates and emphasizes that the foundation of calligraphy lies in classicality, and it is advisable to learn regular script first, then calligraphy and cursive script. He thinks that regular script and cursive script are indispensable, and points out a principle of learning calligraphy step by step. That sentence means (on calligraphy) that people who don't know Confucianism well, staff sergeant and talented students can't talk about this (calligraphy principle).