IMDB Trivia about Buffy being "perpetually 6 years old" is not true

This claim from the IMDB Trivia page is simply not true:

Producer Don Fedderson insisted that the character of Buffy remain perpetually six years old...

This dehumanizing treatment is thought to have contributed to Jones feeling too typecast to continue her acting career. This discouragement also contributed to her dissolute behavior in her teen years until she died of a drug overdose at the age of 18.

In S5, Ep22, Goodbye Mrs. Beasley, Buffy is riding the elevator with the new girl from California, and tells her "I'm Nine years old".