There's another side to things too. 85% of people who applied and got in and decided to go there are from California. Maybe a bunch of east coasters got in but didn't decide to go.
And there may be many, many more OOSers applying, so that even if they interviewed similar numbers of OOS vs IS people, the percentages will be off (e.g. 500 OOS out of 6,000 and 500 IS out of 1,000 - these are random numbers, nothing to do with UCLA)
Lastly, I suspect even though schools say they have "no state preference", they still have to practice yield protection. At the end of the day, people from the state are generally more likely to there for many reasons.