As the article you cited states, the immune system responds differently to different types of antigens. As far as Covid-19 goes, it should be a relatively simple study to determine if antigenic original sin is relevant. Using an updated vaccine, perhaps one that targets the South African variant, compare immune responses in people who were infected with the original virus and people never infected and newly vaccinated. According to the original sin hypothesis, those who were previously infected should produce an immune response preferentially directed towards the original virus, rather than the variant specified in the vaccine.

By the way, when the Nature paper was written, there were limited ways to measure T cell responses. Many more such tools available now.