Hua Tuo wasn't joking when he said that Buddha was a cultivation monster. The ideas Buddha kept suggesting were things the physician had never heard of before. He followed very strictly to the books he read and marital manuals. Cultivation was something that progressed by stages through hard work and talent.
The Enlightened One didn't follow the strict conventional rules that Hua Tuo learnt. In fact, the Sage God of Medicine was wondering if he was severely outdated. He never really kept up with the times but this was just too much. It was as if Buddha told him the world was a pyramid and not a sphere as he always knew it to be.
Simply put it, Hua Tuo was overwhelmed. Buddha just came crashing into his world and pointed out everything was wrong. Now Hua Tuo didn't know what to do with the few centuries worth of cultivation he did. After toiling away for so long, Buddha came in to tell him none of those was really required. The doctor felt depression coming for him.
