He is this both studying at Durham University and in a college.
While you're right the terms are usually used the way you point out in British English, and it would have been unusual for a British article to describe him as a college student because it'd be misleading, if being pedantic the language used is technically correct even when used in the UK. Certainly when writing American English in a US publication about the UK.
[1] Not all, as far as I know. E.g. I don't think LSE or Kings or any of the other former University of London colleges that are now full universities in their own right have their own colleges (they're still part of University of London, but gained the right to apply for university status in 2018) but I might be wrong about that.
[2] https://www.studentgoodguide.com/apply-to-university/best-du...