It says,
"The study, released on Saturday, compared almost 400 people who had tested positive for COVID-19, 14 days or more after they received one or two doses of the vaccine"
and
"The companies said on April 1 that their vaccine was around 91% effective at preventing COVID-19"
COVID-19 is the disease whereas testing checks for presence of portions of the virus. The Phase III clinical trials looked for symptomatic infection. Without details on the clinical progression of the vaccinated who tested positive, there's nothing to see here.
Also,
"But among patients who had received two doses of the vaccine, the variant’s prevalence rate was eight times higher than those unvaccinated - 5.4% versus 0.7%."
This indicates that if the immune system is primed to identify a certain variant, its performance is hindered as opposed to a naive immune system.
The actual paper is at https://www.medrxiv.org/content/10.1101/2021.04.06.21254882v... From what I can tell, the median age of the fully vaccinated is 61 and 46 for the unvaccinated. (table 1). And the comparison for the SA variant is between 8 in the former vs 1 in the latter. Sensationalist reporting.