I think the problem with UCLA is that people are holding acceptances who may not be going. Since UCLA has not made many official offers on Financial aid and scholarships, many people are submitting SIRs, but may withdraw if $$ isn't enough.
Over the weekend, at the admit student day, most of the questions are from people asking when $$ will be offered, and UCLA's response is "soon". I suspect some people will withdraw their acceptance when they don't get the $$ they are looking for and that will free up some spots.