They can be disappointed with the accommodation, but they've made a decision that they aren't so disappointed it's worth making the call. And tbf the accommodations office is probably inundated currently and there's a good chance they'll be told tough luck. It's also quite likely that the stuff from the uni has told them not to call because nothing will be done.
It's just sounds better and gets more sympathy if they are "devastated" and can't phone due to "anxiety". Bit like when OPs here are "crying and shaking".
Dd1 would have decided it wasn't worth the hassle anyway. She doesn't like phoning, but would have weighed up the chance of being changed and decided it wasn't worth the time and energy contesting it.
Dd2, who does have anxiety, probably would have phoned, and with her jammy luck probably got through to the head of accommodation who upgraded her to the top room at no extra expense with a bunch of flowers for the initial disappointment
, but she would be the exception rather than the rule.
Ds wouldn't care what the room was like as long as it had a bed and a desk big enough for 2 screens for his computer, so he wouldn't phone either.
That's definitely personality coming in. My sister would no way have phoned, I probably would have, my brother would have had my mum phoning for him... so very similar distribution.
But they're 18yo, speaking to an adult on the phone. Phoning is used less now because of the ease of texts/messages and emails, so it is more daunting.
They've also had around 2 years out of their lives at a point when they would have been beginning to fledge their wings, get jobs, go out, organise things etc for themselves.