It's not a hard requirement and the prior experience isn't limited to Universal and could be with another similar internship somewhere else -- but yes, they prefer
return candidates as internships are a farm to draw from for their full-time hires after graduation. Also, FWIW, last year's interns probably got the fuzzy end of the lollipop as projects get back-burnered so anyone looking for a real internship opportunity probably needs a second chance.
I know both companies I interned at when I was in college had similar preferences even though it wasn't itemized in the job posting.
I have a friend who started there as an intern in Creative a couple years ago and is currently traveling to China to work on their new Beijing project. Not sure what her availability is the next month or so but if anyone here has questions for someone on the inside, she may be able to respond to questions if anyone wants to know in
advance what it may be like -- at least to the extent her
NDA allows her to speak about the experience.