Even A will lower the capped gpa. eg. 22 semesters all A with 8 honors points capped gpa = 4.36, with 23 semisters all A with 8 honors points capped gpa = 4.34
Ref:
http://collegetools.berkeley.edu/documents/cat_113-128/Calculating_GPA.pdf
http://admission.universityofcalifornia.edu/counselors/q-and-a/calculating-gpa/
In short, students taking more than 4 honor classes (AP, Honors or College course) are penalized in the capped gpa.