SGF parsing - Inconsistency in rules

Hi, it seems there is inconsistency with rules VS test cases in exercise.
So one of the rules is that properties can’t have lower case letters, but some examples from tests were passing even though it had lower case…
I was reading rules of the game and its seems like it shouldn’t be allow to have lower case properties. Can someone shad a bit of a light here ?

The property values are b, d. The all caps property identifiers are A, C.

The tests use “property” to refer to the property identifier here.