At Berkeley, Psych will let you skip the first Biology course with a 4 or 5 from what I understand. I would imagine that UCLA has somewhat similar policies, but hard to say.
Yes, getting null credits is totally different than being able to get credit for a course in a specific department, as all departments have their own rules regarding AP credits fulfilling a class requirement. For example, my kid had a 4 on his AP Bio, which he got credits for, but Data Science would not allow that credit for his lower division domain emphasis class for Computational Biology (needs to take the first class, or take it at CCC). So it becomes pretty much a useless credit, though the credits do go towards your number to graduate if you wind up never taking the class again. If you do take the class again, then the AP credits gets overridden I would think, but if it is unassigned, not sure if it will get overridden.