This study is also pretty old, despite being "published" now. It was originally submitted in June of 2021, and discusses the N501Y (presumably V1, given the timing) variant, which is no longer relevant.

Worse, the vaccinated samples were all gathered by mid-March 2021, and except for three people, all were gathered within 40 days of vaccination. But the median time from symptoms for those who were previously infected was over two hundred days.

This difference alone hopelessly confounds any stated conclusion, yet they've buried this essential information in the supplemental materials (ST1 & 2). This paper is bad.