Unfortunately, this "method" to distinguish "ser" from "estar" based on permanent/changing states is very popular, but inaccurate and it causes a lot of confusion for learners. ;(
"Ser" is used for traits inherent to the subject (like "what someone/something is", "what someone/something is like") and "estar" is for features that aren't intrinsic to the subject (there is a process or an accident that made the subject have this characteristic, or their location --like "how someone is doing", "where someone/something is").
Take a look at
this thread for the differences between "ser" and "estar".