Perhaps you misread the paper? You cherry picked a portion of the abstract and made it seem like that conclusion was made. Here, let me help you:
"Conclusions: Individuals who have had SARS-CoV-2 infection are unlikely to benefit from COVID-19 vaccination, and vaccines can be safely prioritized to those who have not been infected before."
You can prioritize those who have not been infected before BECAUSE those who HAVE been infected are unlikely to see a benefit in vaccinating to begin with.
"Conclusions: Individuals who have had SARS-CoV-2 infection are unlikely to benefit from COVID-19 vaccination, and vaccines can be safely prioritized to those who have not been infected before."
You can prioritize those who have not been infected before BECAUSE those who HAVE been infected are unlikely to see a benefit in vaccinating to begin with.