I would not be surprised if this was true. I found the below link when I first started to apply to programs. According to the document, the rate of completion within 10 years for UCLA is 56%. I don't know how accurate this number is, but it seems that the other information on the document is pretty accurate. With that being said, I still decided to apply to UCLA and would probably still attend if given the opportunity. I don't know how much weight you can put on this, but every encounter I have had with Wendy Fujinami has been really positive. I'd definitely be a little bit worried about the culture at UCLA, but I'd also not rush to any decisions. It seems that your a good fit for both programs, so perhaps the safest option is UC Irvine. But, I wonder what is driving the low completion rate at UCLA, if true, and how your fit with the program might influence your experience with the program.
http://tinyurl.com/pu2feyv