First, the line quoted from the highlights section is referring to the 1054 antibody, which was isolated from a patient infected with SARS-CoV-2, as opposed to one produced from vaccine response[1]. Second, the infection enhancing effect was determined in vitro.
So none of that supports the idea that ADE was actually detected in a human, and particularly the idea that vaccine induced ADE has actually been observed.
All that said, if the results of the paper hold up, they may help explain why the efficacy of the vaccines are reduced in the face of the delta variant. That would be extraordinarily useful in formulating better vaccines, so I'm cheering the science along. I'm less cheerful about the cherry-picking to support anti-vaccine narratives.
[1]: https://www.cell.com/cell/pdf/S0092-8674(21)00756-X.pdf