In the Japanese dub, is there any parallel to Baobao's use of Sichuanese?
I watched the first three episodes of Hitori no Shita, and can confirm that Baobao speaks plain old standard Japanese (hyoujungo), with not a hint of any regional lect. In episode 2, Chulan indeed only states that the details she's reading out are obvious lies.

(It came as a surprise when I learned that she spoke a non-standard variety in the Chinese audio version. Kinda strange that they wouldn't similarly pick a non-standard variety of Japanese for the Japanese version.)