All UK universities do this. Not necessarily a bad thing unlike how the article portrays it. PhD students (and depending on the institution, postdocs) in the UK get a stipend that has no mandated teaching hours. Teaching allows PhD students to earn some extra income within the university. We certainly still have a compensation problem in academia. Bright STEM PhD grads don't want to earn £30-40k as a postdoc when ear…
When I did it, I had my DPhil grant/post-doc salary and it felt like side money rather than being my 'job' and I was partly doing for the experience, for my CV (good to be able to put 'Lecturer at Oxford' on it!) and partly because I enjoyed it. I felt quite lucky to be offered tutoring jobs at Oxford as they were much sought-after by DPhil students.
I think it's also worth pointing out that not all Oxford colleges are 'rich' and many have buildings and grounds that are expensive to maintain. I don't think most of them are better placed to pay more than other UK universities.
There's an argument to be made that people teaching at universities should be paid more, but it does feel unfair to single out Oxford.