Correct. There was another with a nativity scene that passed muster because it was in a commercial shopping area, albeit public property, and included other displays with Christmas trees and Santa Claus.There is a long history of establishment clause cases that makes this very point.
To keep it simple, the first test in establishment cases is 1) does it (the law) have a secular purpose? Clearly, there is nothing secular about the commandments about religion.
A different decision was reached in a case in which the 10 Commandments was included in a historical display on the grounds of the Texas Capitol showing its past history. The commandments was only one display out of several.
This LA stunt is entirely different.